{"id":46207,"date":"2023-06-01T18:03:20","date_gmt":"2023-06-01T09:03:20","guid":{"rendered":"https:\/\/kinsta.com\/jp\/?p=46207&#038;preview=true&#038;preview_id=46207"},"modified":"2023-08-28T19:02:15","modified_gmt":"2023-08-28T10:02:15","slug":"javascript-react","status":"publish","type":"post","link":"https:\/\/kinsta.com\/jp\/blog\/javascript-react\/","title":{"rendered":"React\u3092\u4f7f\u3044\u3053\u306a\u3059\u305f\u3081\u306b\u77e5\u3063\u3066\u304a\u304d\u305f\u3044JavaScript\u306e\u6a5f\u80fd"},"content":{"rendered":"<p><a href=\"https:\/\/kinsta.com\/jp\/topics\/react\/\">React<\/a>\u306f\u6700\u8fd1\u4eba\u6c17\u306e<a href=\"https:\/\/kinsta.com\/jp\/blog\/javascript-libraries\/\">JavaScript\u30e9\u30a4\u30d6\u30e9\u30ea<\/a>\u3067\u3059\u3002\u30c0\u30a4\u30ca\u30df\u30c3\u30af\u304b\u3064\u30ec\u30b9\u30dd\u30f3\u30b7\u30d6\u306a\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u306e\u4f5c\u6210\u306b\u4f7f\u7528\u3067\u304d\u3001\u9ad8\u3044\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u8a87\u308a\u3001\u7c21\u5358\u306b\u62e1\u5f35\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u57fa\u672c\u7684\u306a\u30ed\u30b8\u30c3\u30af\u306f\u3001\u4f7f\u3044\u56de\u3057\u306e\u3067\u304d\u308b\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u57fa\u3065\u304f\u3082\u306e\u3067\u3001\u540c\u3058\u30b3\u30fc\u30c9\u3092\u4f55\u5ea6\u3082\u66f8\u304f\u624b\u9593\u3092\u524a\u6e1b\u53ef\u80fd\u3067\u3059\u3002\u3064\u307e\u308a\u3001React\u3092\u4f7f\u3048\u3070\u3001<a href=\"https:\/\/kinsta.com\/jp\/topics\/react\/\">\u52b9\u7387\u7684\u306b\u5f37\u529b\u306a\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3<\/a>\u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u306e\u4f5c\u6210\u65b9\u6cd5\u3092\u5b66\u3076\u306a\u3089\u4eca\u3067\u3059\u3002<\/p>\n<p>\u3057\u304b\u3057\u3001<a href=\"https:\/\/kinsta.com\/javascript\/\">JavaScript<\/a>\u306e\u4e3b\u8981\u306a\u6a5f\u80fd\u3092\u3057\u3063\u304b\u308a\u7406\u89e3\u3057\u3066\u3044\u306a\u3044\u3068\u3001React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u306e\u69cb\u7bc9\u306f\u56f0\u96e3\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>\u3053\u306e\u305f\u3081\u3001React\u3092\u4f7f\u3044\u59cb\u3081\u308b\u524d\u306b\u77e5\u3063\u3066\u304a\u304f\u3079\u304dJavaScript\u306e\u6a5f\u80fd\u3068\u6982\u5ff5\u3092\u3054\u7d39\u4ecb\u3057\u307e\u3059\u3002\u3053\u308c\u3092\u3088\u304f\u7406\u89e3\u3059\u308c\u3070\u3001\u9ad8\u5ea6\u306aReact\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u7c21\u5358\u306b\u69cb\u7bc9\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308b\u306f\u305a\u3067\u3059\u3002<\/p>\n<p>\u305d\u308c\u3067\u306f\u3001\u4ee5\u4e0b\u306e\u76ee\u6b21\u306b\u6cbf\u3063\u3066\u9032\u3093\u3067\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n<div><\/div><kinsta-auto-toc heading=\"Table of Contents\" exclude=\"last\" list-style=\"arrow\" selector=\"h2\" count-number=\"-1\"><\/kinsta-auto-toc>\n<h2>JavaScript\u3068ECMAScript<\/h2>\n<p><a href=\"https:\/\/kinsta.com\/jp\/blog\/what-is-javascript\/\">JavaScript<\/a>\u306f<a href=\"https:\/\/kinsta.com\/jp\/blog\/what-is-html\/\">HTML<\/a>\u3084CSS\u3068\u3068\u3082\u306b\u3001\u52d5\u7684\u306a\u30a6\u30a7\u30d6\u30da\u30fc\u30b8\u3092\u69cb\u7bc9\u3059\u308b\u306e\u306b\u4f7f\u7528\u3055\u308c\u308b\u4e00\u822c\u7684\u306a\u30b9\u30af\u30ea\u30d7\u30c8\u8a00\u8a9e\u3067\u3059\u3002HTML\u306f\u30a6\u30a7\u30d6\u30da\u30fc\u30b8\u306e\u69cb\u9020\u3092\u3001CSS\u306f\u305d\u306e\u8981\u7d20\u306e\u30b9\u30bf\u30a4\u30eb\u3084\u30ec\u30a4\u30a2\u30a6\u30c8\u3092\u4f5c\u6210\u3059\u308b\u306e\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u304c\u3001JavaScript\u306f\u30da\u30fc\u30b8\u306b\u52d5\u304d\u3092\u8ffd\u52a0\u3059\u308b\u3001\u3064\u307e\u308a\u6a5f\u80fd\u3084\u30a4\u30f3\u30bf\u30e9\u30af\u30c6\u30a3\u30d6\u6027\u3092\u3082\u305f\u3089\u3059\u8a00\u8a9e\u3067\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f JavaScript\u306f\u30011995\u5e74\u306bNetscape Communications\u306e\u30d6\u30ec\u30f3\u30c0\u30f3\u30fb\u30a2\u30a4\u30af\u6c0f\u306b\u3088\u3063\u3066\u3001Netscape Navigator\u30d6\u30e9\u30a6\u30b6\u306e\u30a6\u30a7\u30d6\u30da\u30fc\u30b8\u306b\u30a4\u30f3\u30bf\u30e9\u30af\u30c6\u30a3\u30d6\u6027\u3092\u6301\u305f\u305b\u308b\u3053\u3068\u3092\u76ee\u7684\u3068\u3057\u3066\u958b\u767a\u3055\u308c\u307e\u3057\u305f\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u305d\u306e\u5f8c\u3001\u3053\u306e\u8a00\u8a9e\u306f\u4e3b\u8981\u306a\u30d6\u30e9\u30a6\u30b6\u306b\u63a1\u7528\u3055\u308c\u3001JavaScript\u306e\u52d5\u4f5c\u3092\u8a18\u8ff0\u3059\u308b\u6587\u66f8\u3001<a href=\"https:\/\/en.wikipedia.org\/wiki\/ECMAScript\" target=\"_blank\" rel=\"noopener noreferrer\">ECMAScript<\/a>\u304c\u4f5c\u6210\u3055\u308c\u307e\u3057\u305f\u3002<\/p>\n<p>ECMAScript\u306f\u57fa\u672c\u7684\u306b\u306f\u6bce\u5e74\u66f4\u65b0\u3055\u308c\u3066\u304a\u308a\u3001JavaScript\u306b\u306f\u305d\u306e\u90fd\u5ea6\u65b0\u3057\u3044\u6a5f\u80fd\u304c\u8ffd\u52a0\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p><a href=\"https:\/\/262.ecma-international.org\/6.0\/\" target=\"_blank\" rel=\"noopener noreferrer\">ECMAScript 2015<\/a>\u306f\u6a19\u6e96\u306e6\u756a\u76ee\u306e\u30ea\u30ea\u30fc\u30b9\u3067\u3042\u308b\u305f\u3081\u3001<strong>ES6<\/strong>\u3068\u3082\u547c\u3070\u308c\u307e\u3059\u3002\u305d\u308c\u4ee5\u964d\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\u306f\u9032\u884c\u5f62\u3067\u8868\u8a18\u3055\u308c\u308b\u305f\u3081\u3001ECMAScript 2016\u3092ES7\u3001ECMAScript 2017\u3092ES8\u3001\u3068\u3044\u3063\u305f\u5177\u5408\u306b\u8868\u8a18\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u898f\u683c\u306b\u65b0\u6a5f\u80fd\u304c\u8ffd\u52a0\u3055\u308c\u308b\u983b\u5ea6\u304c\u9ad8\u3044\u305f\u3081\u3001\u3059\u3079\u3066\u306e\u30d6\u30e9\u30a6\u30b6\u3067\u30b5\u30dd\u30fc\u30c8\u3055\u308c\u3066\u3044\u306a\u3044\u3082\u306e\u3082\u3042\u308a\u307e\u3059\u3002\u3067\u306f\u3001JS\u30a2\u30d7\u30ea\u306b\u8ffd\u52a0\u3057\u305f\u6700\u65b0\u306eJavaScript\u6a5f\u80fd\u304c\u3001\u3059\u3079\u3066\u306e\u30a6\u30a7\u30d6\u30d6\u30e9\u30a6\u30b6\u3067\u671f\u5f85\u901a\u308a\u306b\u52d5\u4f5c\u3059\u308b\u305f\u3081\u306b\u306f\u3001\u3069\u3046\u3059\u308c\u3070\u3088\u3044\u306e\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n<p>\u9078\u629e\u80a2\u306f3\u3064\u3042\u308a\u307e\u3059\u3002<\/p>\n<ol>\n<li>\u3059\u3079\u3066\u306e\u4e3b\u8981\u306a\u30d6\u30e9\u30a6\u30b6\u304c\u65b0\u6a5f\u80fd\u3092\u30b5\u30dd\u30fc\u30c8\u3059\u308b\u3088\u3046\u306b\u306a\u308b\u307e\u3067\u5f85\u3064\u3002\u3057\u304b\u3057\u3001\u958b\u767a\u4e2d\u306e\u30a2\u30d7\u30ea\u306b\u305d\u306eJS\u306e\u65b0\u6a5f\u80fd\u304c\u7d76\u5bfe\u306b\u5fc5\u8981\u306a\u5834\u5408\u3001\u3053\u308c\u306f\u9078\u3076\u3079\u304d\u9078\u629e\u80a2\u3067\u306f\u3042\u308a\u307e\u305b\u3093\u3002<\/li>\n<li>\u30dd\u30ea\u30d5\u30a3\u30eb\u3092\u5229\u7528\u3059\u308b\u3002\u3064\u307e\u308a\u3001\u300c\u30cd\u30a4\u30c6\u30a3\u30d6\u306b\u5bfe\u5fdc\u3057\u3066\u3044\u306a\u3044\u53e4\u3044\u30d6\u30e9\u30a6\u30b6\u3067\u6700\u65b0\u306e\u6a5f\u80fd\u3092\u5229\u7528\u3059\u308b\u305f\u3081\u306e\u30b3\u30fc\u30c9\uff08\u901a\u5e38\u306f\u30a6\u30a7\u30d6\u4e0a\u306eJavaScript\uff09\u300d\u3092\u4f7f\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\uff08<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Polyfill\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u3082\u53c2\u7167\u306e\u3053\u3068\uff09\u3002<\/li>\n<li><a href=\"https:\/\/babeljs.io\/docs\/\" target=\"_blank\" rel=\"noopener noreferrer\">Babel<\/a>\u3084<a href=\"https:\/\/github.com\/google\/traceur-compiler\" target=\"_blank\" rel=\"noopener noreferrer\">Traceur<\/a> \u306a\u3069\u3001ECMAScript 2015+\u306e\u30b3\u30fc\u30c9\u3092\u3059\u3079\u3066\u306e\u30d6\u30e9\u30a6\u30b6\u3067\u30b5\u30dd\u30fc\u30c8\u3055\u308c\u3066\u3044\u308bJavaScript\u30d0\u30fc\u30b8\u30e7\u30f3\u306b\u5909\u63db\u3059\u308bJavaScript\u30c8\u30e9\u30f3\u30b9\u30d1\u30a4\u30e9\u3092\u4f7f\u7528\u3059\u308b\u3002<\/li>\n<\/ol>\n\n<h2>\u6587\u3068\u5f0f\u306e\u9055\u3044<\/h2>\n<p>React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u69cb\u7bc9\u3059\u308b\u969b\u306b\u306f\u3001\u6587\u3068\u5f0f\u306e\u9055\u3044\u3092\u7406\u89e3\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002\u305d\u3053\u3067\u3001\u5c11\u3057\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306e\u57fa\u672c\u7684\u306a\u6982\u5ff5\u306b\u7acb\u3061\u8fd4\u3063\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<p>\u30b3\u30f3\u30d4\u30e5\u30fc\u30bf\u30d7\u30ed\u30b0\u30e9\u30e0\u306f\u3001\u30b3\u30f3\u30d4\u30e5\u30fc\u30bf\u304c\u5b9f\u884c\u3059\u308b\u547d\u4ee4\u3067\u3059\u3002\u3053\u306e\u547d\u4ee4\u306f<strong>\u6587\uff08\u30b9\u30c6\u30fc\u30c8\u30e1\u30f3\u30c8\uff09<\/strong>\u3068\u547c\u3070\u308c\u307e\u3059\u3002<\/p>\n<p>\u6587\u3068\u306f\u7570\u306a\u308a\u3001<strong>\u5f0f\uff08\u30a8\u30af\u30b9\u30d7\u30ec\u30c3\u30b7\u30e7\u30f3\uff09<\/strong>\u306f\u5024\u3092\u751f\u6210\u3059\u308b\u30b3\u30fc\u30c9\u306e\u65ad\u7247\u3067\u3059\u3002\u6587\u306b\u304a\u3044\u3066\u3001\u5f0f\u306f\u5024\u3092\u8fd4\u3059\u90e8\u5206\u3067\u3042\u308a\u3001\u901a\u5e38\u3001\u7b49\u53f7\u306e\u53f3\u5074\u306b\u5f0f\u304c\u4f4d\u7f6e\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u6587\u3068\u306f\u3001\u4f55\u304b\u3092\u884c\u3046\u30b3\u30fc\u30c9\u306e\u30d6\u30ed\u30c3\u30af\u3092\u6307\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u305d\u308c\u306b\u5bfe\u3057\u3066<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u5f0f\u306f\u3001\u5024\u3092\u751f\u6210\u3059\u308b\u30b3\u30fc\u30c9\u306e\u65ad\u7247\u3092\u6307\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>JavaScript\u306e\u6587\u306f\u3001\u901a\u5e38\u30bb\u30df\u30b3\u30ed\u30f3\u3067\u7d42\u308f\u308b\u304b\u3001\u4e2d\u62ec\u5f27\u3067\u56f2\u307e\u308c\u305f\u30b3\u30fc\u30c9\u306e\u30d6\u30ed\u30c3\u30af\u307e\u305f\u306f\u884c\u306b\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306f\u3001JavaScript\u306e\u6587\u306e\u7c21\u5358\u306a\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-js\">document.getElementById(\"hello\").innerHTML = \"Hello World!\";<\/code><\/pre>\n<p>\u4e0a\u8a18\u306e\u6587\u306f\u3001<code>\"Hello World!\"<\/code>\u3092<code>id=\"hello\"<\/code>\u306eDOM\u8981\u7d20\u306b\u66f8\u304d\u8fbc\u3093\u3067\u3044\u307e\u3059\u3002<\/p>\n<p>\u3059\u3067\u306b\u8ff0\u3079\u305f\u3088\u3046\u306b\u3001\u5f0f\u306f\u5024\u3092\u751f\u6210\u3059\u308b\u304b\u3001\u305d\u308c\u81ea\u4f53\u304c\u5024\u3067\u3059\u3002\u6b21\u306e\u3088\u3046\u306a\u4f8b\u3092\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-js\">msg = document.getElementById(\"hello\").value;<\/code><\/pre>\n<p><code>document.getElementById(\"hello\").value<\/code>\u306f\u3001\u5024\u3092\u8fd4\u3059\u306e\u3067\u5f0f\u3067\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306e\u4f8b\u3067\u3001\u5f0f\u3068\u6587\u306e\u9055\u3044\u304c\u3055\u3089\u306b\u660e\u78ba\u306b\u306a\u308b\u306f\u305a\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const msg = \"Hello World!\";\nfunction sayHello( msg ) {\n\tconsole.log( msg );\n}<\/code><\/pre>\n<p>\u4e0a\u306e\u4f8b\u3067\u306f<\/p>\n<ul>\n<li>\u6700\u521d\u306e\u884c\u306f\u6587\u3067\u3001<code>\"Hello World!\"<\/code>\u306f\u5f0f\u3067\u3059\u3002<\/li>\n<li>\u95a2\u6570\u5ba3\u8a00\u306f\u6587\u3067\u3001\u95a2\u6570\u306b\u6e21\u3055\u308c\u308b\u30d1\u30e9\u30e1\u30fc\u30bf<code>msg<\/code>\u306f\u5f0f\u3067\u3059\u3002<\/li>\n<li>\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u30e1\u30c3\u30bb\u30fc\u30b8\u3092\u8868\u793a\u3059\u308b\u884c\u306f\u6587\u3067\u3001\u3053\u3053\u3067\u3082\u30d1\u30e9\u30e1\u30fc\u30bf<code>msg<\/code>\u306f\u5f0f\u3067\u3059\u3002<\/li>\n<\/ul>\n<h3>React\u3067\u5f0f\u304c\u91cd\u8981\u306a\u7406\u7531<\/h3>\n<p><a href=\"https:\/\/kinsta.com\/jp\/blog\/react-best-practices\/\">React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u69cb\u7bc9<\/a>\u3059\u308b\u969b\u3001<a href=\"https:\/\/react.dev\/learn\/javascript-in-jsx-with-curly-braces\" target=\"_blank\" rel=\"noopener noreferrer\">JavaScript\u306e\u5f0f\u3092JSX\u30b3\u30fc\u30c9\u306b\u633f\u5165<\/a>\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u4f8b\u3048\u3070\u3001\u5909\u6570\u3092\u6e21\u3057\u305f\u308a\u3001\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u3084\u6761\u4ef6\u3092\u66f8\u3044\u305f\u308a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u3053\u308c\u3092\u884c\u3046\u306b\u306f\u3001JS\u30b3\u30fc\u30c9\u3092\u4e2d\u62ec\u5f27\u3067\u56f2\u3080\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u4f8b\u3048\u3070\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u5909\u6570\u3092\u6e21\u3059\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const Message = () =&gt; {\n\tconst name = \"Carlo\";\n\treturn &lt;p&gt;Welcome {name}!&lt;\/p&gt;;\n}<\/code><\/pre>\n<p>\u3064\u307e\u308a\u3001\u4e2d\u62ec\u5f27\u306f\u30c8\u30e9\u30f3\u30b9\u30d1\u30a4\u30e9\u306b\u3001\u4e2d\u62ec\u5f27\u3067\u56f2\u307e\u308c\u305f\u30b3\u30fc\u30c9\u3092JS\u30b3\u30fc\u30c9\u3068\u3057\u3066\u51e6\u7406\u3059\u308b\u3088\u3046\u306b\u6307\u793a\u3059\u308b\u5f79\u5272\u3092\u679c\u305f\u3057\u307e\u3059\u3002<code>&lt;p&gt;<\/code>\u30bf\u30b0\u306e\u524d\u3068\u3001<code>&lt;\/p&gt;<\/code>\u30bf\u30b0\u306e\u5f8c\u306b\u6765\u308b\u3082\u306e\u306f\u3059\u3079\u3066\u3001\u901a\u5e38\u306eJavaScript\u30b3\u30fc\u30c9\u3067\u3059\u3002<code>&lt;p&gt;<\/code>\u30bf\u30b0\u3068<code>&lt;\/p&gt;<\/code>\u30bf\u30b0\u306e\u4e2d\u306b\u3042\u308b\u3082\u306e\u306f\u3001\u3059\u3079\u3066JSX\u30b3\u30fc\u30c9\u3068\u3057\u3066\u51e6\u7406\u3055\u308c\u307e\u3059\u3002<\/p>\n<p>\u5225\u306e\u4f8b\u3092\u6319\u3052\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">const Message = () =&gt; {\t\n\tconst name = \"Ann\";\n\tconst heading = &lt;h3&gt;Welcome {name}&lt;\/h3&gt;;\n\treturn (\n\t\t&lt;div&gt;\n\t\t\t{heading}\n\t\t\t&lt;p&gt;This is your dashboard.&lt;\/p&gt;\n\t\t&lt;\/div&gt;\n\t);\n}<\/code><\/pre>\n<p>\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u6e21\u3059\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">render(){\t\t\t\n\tconst person = {\n\t\tname: 'Carlo',\n\t\tavatar: 'https:\/\/en.gravatar.com\/userimage\/954861\/fc68a728946aac04f8531c3a8742ac22',\n\t\tdescription: 'Content Writer'\n\t}\n\n\treturn (\n\t\t&lt;div&gt;\n\t\t\t&lt;h2&gt;Welcome {person.name}&lt;\/h2&gt;\n\t\t\t&lt;img\n\t\t\t\tclassName=\"card\"\n\t\t\t\tsrc={person.avatar}\n\t\t\t\talt={person.name}\n\t\t\t\/&gt;\n\t\t\t&lt;p&gt;Description: {person.description}.&lt;\/p&gt;\n\t\t&lt;\/div&gt;\n\t);\n}<\/code><\/pre>\n<p>\u307e\u305f\u3001\u4ee5\u4e0b\u306f\u3082\u3046\u5c11\u3057\u5206\u304b\u308a\u3084\u3059\u3044\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">render(){\n\tconst person = {\n\t\tname: 'Carlo',\n\t\tavatar: 'https:\/\/en.gravatar.com\/userimage\/954861\/fc68a728946aac04f8531c3a8742ac22?size=original',\n\t\tdescription: 'Content Writer',\n\t\ttheme: {\n\t\t\tboxShadow: '0 4px 8px 0 rgba(0,0,0,0.2)', width: '200px'\n\t\t}\n\t}\n\n\treturn (\n\t\t&lt;div style={person.theme}&gt;\n\t\t\t&lt;img\n\t\t\t\tsrc={person.avatar}\n\t\t\t\talt={person.name}\n\t\t\t\tstyle={ { width: '100%' } }\n\t\t\t\/&gt;\n\t\t\t&lt;div style={ { padding: '2px 16px' } }&gt;\n\t\t\t\t&lt;h3&gt;{person.name}&lt;\/h3&gt;\n\t\t\t\t&lt;p&gt;{person.description}.&lt;\/p&gt;\n\t\t\t&lt;\/div&gt;\n\t\t&lt;\/div&gt;\n\t);\n}<\/code><\/pre>\n<p>\u8981\u7d20<code>img<\/code>\u3068<code>div<\/code>\u306e<code>style<\/code>\u5c5e\u6027\u306b\u4e8c\u91cd\u306e\u4e2d\u62ec\u5f27\u304c\u3042\u308b\u3053\u3068\u306b\u6ce8\u76ee\u3057\u3066\u304f\u3060\u3055\u3044\u3002\u30ab\u30fc\u30c9\u306e\u30b9\u30bf\u30a4\u30eb\u3068\u753b\u50cf\u306e\u30b9\u30bf\u30a4\u30eb\u3092\u542b\u30802\u3064\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u6e21\u3059\u305f\u3081\u306b\u4e8c\u91cd\u62ec\u5f27\u3092\u4f7f\u7528\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<figure id=\"attachment_152320\" aria-describedby=\"caption-attachment-152320\" style=\"width: 1360px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-152320\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/card-example.jpg\" alt=\"React\u3067\u4f5c\u6210\u3057\u305f\u30ab\u30fc\u30c9\u306e\u4f8b\" width=\"1360\" height=\"694\"><figcaption id=\"caption-attachment-152320\" class=\"wp-caption-text\">React\u3067\u4f5c\u6210\u3057\u305f\u30ab\u30fc\u30c9\u306e\u4f8b<\/figcaption><\/figure>\n<p>\u4e0a\u8a18\u306e\u3059\u3079\u3066\u306e\u4f8b\u3067\u3001<a href=\"https:\/\/kinsta.com\/jp\/blog\/what-is-jsx\/\">JSX<\/a>\u306bJavaScript\u306e\u5f0f\u304c\u542b\u307e\u308c\u3066\u3044\u308b\u3053\u3068\u306b\u304a\u6c17\u3065\u304d\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f JSX\u306f\u3001\u4e2d\u62ec\u5f27\u3067\u56f2\u307e\u308c\u305fJavaScript\u306e\u8868\u73fe\u3057\u304b\u53d7\u3051\u4ed8\u3051\u307e\u305b\u3093\u3002JSX\u306e\u30b3\u30fc\u30c9\u5185\u306b\u6587\u3092\u8a18\u8ff0\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002<\/strong><\/p>\n<p><strong>\u3053\u308c\u306b\u306f\u6b21\u306e\u3088\u3046\u306a\u3082\u306e\u304c\u3042\u308a\u307e\u3059\u3002<\/strong><\/p>\n<ul>\n<li><strong>\u5909\u6570<\/strong><\/li>\n<li><strong>\u5f15\u7528\u7b26\u3067\u56f2\u307e\u308c\u305f\u6587\u5b57\u5217<\/strong><\/li>\n<li><strong>\u95a2\u6570\u547c\u3073\u51fa\u3057<\/strong><\/li>\n<li><strong>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8<\/strong><\/li>\n<li><strong>\u6761\u4ef6\u5f0f<\/strong><\/li>\n<\/ul>\n<p><\/p>\n<\/aside>\n\n<h2>React\u306b\u304a\u3051\u308b\u4e0d\u5909\u6027<\/h2>\n<p>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u6307\u5411\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u3068\u95a2\u6570\u578b\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306b\u306f\u3001\u4e0d\u5909\u6027\u3068\u5909\u6027\u3068\u3044\u3046<a href=\"https:\/\/en.wikipedia.org\/wiki\/Immutable_object\" target=\"_blank\" rel=\"noopener noreferrer\">2\u3064\u306e\u91cd\u8981\u306a\u6982\u5ff5<\/a>\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u4e0d\u5909\u6027\u306f\u3001\u5024\u304c\u4f5c\u6210\u3055\u308c\u305f\u5f8c\u306b\u5909\u66f4\u3067\u304d\u306a\u3044\u3053\u3068\u3092\u610f\u5473\u3057\u307e\u3059\u3002\u4e00\u65b9\u3067\u5909\u6027\u3068\u306f\u3001\u3082\u3061\u308d\u3093\u305d\u306e\u9006\u3092\u610f\u5473\u3057\u307e\u3059\u3002<\/p>\n<p>JavaScript\u3067\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Primitive\" target=\"_blank\" rel=\"noopener noreferrer\">\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u5024<\/a>\u306f <a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Immutable\" target=\"_blank\" rel=\"noopener noreferrer\">\u4e0d\u5909<\/a>\u3067\u3042\u308a\u3001\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u5024\u3092\u4e00\u5ea6\u4f5c\u6210\u3059\u308b\u3068\u5909\u66f4\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u305b\u3093\u3002\u9006\u306b\u3001\u914d\u5217\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306f\u3001\u65b0\u3057\u3044\u5024\u3092\u518d\u3073\u5272\u308a\u5f53\u3066\u3059\u308b\u3053\u3068\u306a\u304f\u3001\u30d7\u30ed\u30d1\u30c6\u30a3\u3084\u8981\u7d20\u3092\u5909\u66f4\u3067\u304d\u308b\u305f\u3081\u3001\u5909\u6027\u3068\u3044\u3046\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>JavaScript\u3067\u4e0d\u5909\u6027\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f7f\u7528\u3059\u308b\u7406\u7531\u306f\u3044\u304f\u3064\u304b\u3042\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u5411\u4e0a<\/li>\n<li>\u30e1\u30e2\u30ea\u6d88\u8cbb\u91cf\u306e\u524a\u6e1b<\/li>\n<li>\u30b9\u30ec\u30c3\u30c9\u30bb\u30fc\u30d5<\/li>\n<li>\u30b3\u30fc\u30c7\u30a3\u30f3\u30b0\u3068\u30c7\u30d0\u30c3\u30b0\u304c\u5bb9\u6613\u306b\u306a\u308b<\/li>\n<\/ul>\n<p>\u4e0d\u5909\u6027\u306e\u30d1\u30bf\u30fc\u30f3\u306b\u5f93\u3063\u3066\u3001\u5909\u6570\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304c\u4e00\u5ea6\u5272\u308a\u5f53\u3066\u3089\u308c\u308b\u3068\u3001\u518d\u5272\u308a\u5f53\u3066\u3084\u5909\u66f4\u304c\u3067\u304d\u307e\u305b\u3093\u3002\u30c7\u30fc\u30bf\u3092\u5909\u66f4\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b\u5834\u5408\u306f\u3001\u305d\u306e\u30b3\u30d4\u30fc\u3092\u4f5c\u6210\u3057\u3001\u5143\u306e\u5185\u5bb9\u3092\u5909\u66f4\u305b\u305a\u306b\u3001\u305d\u306e\u5185\u5bb9\u3092\u8abf\u6574\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p><strong>\u4e0d\u5909\u6027<\/strong>\u306fReact\u306e\u30ad\u30fc\u30b3\u30f3\u30bb\u30d7\u30c8\u3067\u3082\u3042\u308a\u307e\u3059\u3002<\/p>\n<p><a href=\"https:\/\/react.dev\/reference\/react\/Component#state\" target=\"_blank\" rel=\"noopener noreferrer\">React\u306e\u30c9\u30ad\u30e5\u30e1\u30f3\u30c8<\/a>\u3067\u306f\u3001\u6b21\u306e\u3088\u3046\u306b\u8aac\u660e\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<blockquote><p>\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u72b6\u614b\u306f\u3001<code>this.state<\/code>\u3068\u3057\u3066\u5229\u7528<span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">\u3067\u304d\u307e\u3059\u3002<\/span><span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">state\u30d5\u30a3\u30fc\u30eb\u30c9\u306f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3067\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002\u72b6\u614b\u3092\u76f4\u63a5\u5909\u7570\u3055\u305b\u306a\u3044\u3067\u304f\u3060\u3055\u3044\u3002\u72b6\u614b\u3092\u5909\u66f4\u3059\u308b\u306b\u306f\u3001\u65b0\u3057\u3044\u72b6\u614b\u3092\u6307\u5b9a\u3057\u3066<\/span><code>setState<\/code><span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">\u3092\u547c\u3073\u51fa\u3057\u307e\u3059\u3002<\/span><\/p><\/blockquote>\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u72b6\u614b\u304c\u5909\u308f\u308b\u305f\u3073\u306b\u3001React\u306f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3057\u3066\u4eee\u60f3DOM\u3092\u66f4\u65b0\u3059\u308b\u304b\u3069\u3046\u304b\u8003\u616e\u3057\u307e\u3059\u3002React\u304c\u4ee5\u524d\u306e\u72b6\u614b\u3092\u628a\u63e1\u3057\u3066\u3044\u306a\u3051\u308c\u3070\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3059\u308b\u304b\u3069\u3046\u304b\u3092\u5224\u65ad\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002React\u306e\u30c9\u30ad\u30e5\u30e1\u30f3\u30c8\u306b\u306f\u3001<a href=\"https:\/\/react.dev\/learn\/updating-objects-in-state#treat-state-as-read-only\" target=\"_blank\" rel=\"noopener noreferrer\">\u308f\u304b\u308a\u3084\u3059\u3044\u4f8b<\/a>\u304c\u8a18\u8f09\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>React\u3067\u72b6\u614b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u4e0d\u5909\u6027\u3092\u4fdd\u8a3c\u3059\u308b\u306b\u306f\u3001\u3069\u306e\u3088\u3046\u306aJavaScript\u306e\u6a5f\u80fd\u3092\u4f7f\u3048\u3070\u3088\u3044\u306e\u3067\u3057\u3087\u3046\u304b\u3002\u5177\u4f53\u7684\u306b\u898b\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<h3>\u5909\u6570\u306e\u5ba3\u8a00<\/h3>\n<p>JavaScript\u3067\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u306b\u306f\u30013\u3064\u306e\u65b9\u6cd5\u304c\u3042\u308a\u307e\u3059\u3002<code>var<\/code>\u3001<code>let<\/code>\u3001<code>const<\/code>\u3067\u3059\u3002<\/p>\n<p><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/var#var_hoisting\" target=\"_blank\" rel=\"noopener noreferrer\"><code>var<\/code><\/a>\u306f\u3001JavaScript\u306e\u521d\u671f\u304b\u3089\u5b58\u5728\u3057\u307e\u3059\u3002\u3053\u308c\u306f\u3001\u95a2\u6570\u30b9\u30b3\u30fc\u30d7\u307e\u305f\u306f\u30b0\u30ed\u30fc\u30d0\u30eb\u30b9\u30b3\u30fc\u30d7\u306e\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u3001\u30aa\u30d7\u30b7\u30e7\u30f3\u3067\u305d\u308c\u3092\u5024\u306b\u521d\u671f\u5316\u3057\u307e\u3059\u3002<\/p>\n<p><code>var<\/code>\u3092\u4f7f\u3063\u3066\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u3068\u3001\u30b0\u30ed\u30fc\u30d0\u30eb\u30b9\u30b3\u30fc\u30d7\u3068\u30ed\u30fc\u30ab\u30eb\u30b9\u30b3\u30fc\u30d7\u306e\u4e21\u65b9\u3067\u3001\u305d\u306e\u5909\u6570\u3092\u518d\u3073\u5ba3\u8a00\u3057\u305f\u308a\u66f4\u65b0\u3057\u305f\u308a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u3088\u3046\u306a\u30b3\u30fc\u30c9\u304c\u8003\u3048\u3089\u308c\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Declare a variable\nvar msg = \"Hello!\";\n\n\/\/ Redeclare the same variable\nvar msg = \"Goodbye!\"\n\n\/\/ Update the variable\nmsg = \"Hello again!\"<\/code><\/pre>\n<p><code>var<\/code>\u306f\u3001\u30b3\u30fc\u30c9\u304c\u5b9f\u884c\u3055\u308c\u308b\u524d\u306b\u51e6\u7406\u3055\u308c\u307e\u3059\u3002\u305d\u306e\u7d50\u679c\u3001\u30b3\u30fc\u30c9\u5185\u306e\u4efb\u610f\u306e\u5834\u6240\u3067\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u3053\u3068\u306f\u3001\u5148\u982d\u3067\u5ba3\u8a00\u3059\u308b\u3053\u3068\u3068\u540c\u3058\u306b\u306a\u308a\u307e\u3059\u3002\u3053\u306e\u52d5\u4f5c\u3092<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Hoisting\" target=\"_blank\" rel=\"noopener noreferrer\">\u30db\u30a4\u30b9\u30c6\u30a3\u30f3\u30b0\uff08\u5dfb\u304d\u4e0a\u3052\uff09<\/a>\u3068\u547c\u3073\u307e\u3059\u3002<\/p>\n<p>\u6ce8\u76ee\u3059\u3079\u304d\u70b9\u3068\u3057\u3066\u3001\u5909\u6570\u306e\u5ba3\u8a00\u3060\u3051\u304c\u30db\u30a4\u30b9\u30c8\u3055\u308c\u3001\u521d\u671f\u5316\u306f\u3055\u308c\u307e\u305b\u3093\u3002\u3053\u308c\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Control_flow\" target=\"_blank\" rel=\"noopener noreferrer\">\u5236\u5fa1\u30d5\u30ed\u30fc<\/a>\u304c\u8a72\u5f53\u3059\u308b\u4ee3\u5165\u6587\u306b\u5230\u9054\u3057\u305f\u3068\u304d\u306b\u8d77\u3053\u308a\u307e\u3059\u3002\u305d\u306e\u6642\u70b9\u307e\u3067\u3001\u5909\u6570\u306f<code>undefined<\/code>\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">console.log(msg); \/\/ undefined\nvar msg = \"Hello!\";\nconsole.log(msg); \/\/ Hello!<\/code><\/pre>\n<p>JS\u95a2\u6570\u5185\u3067\u5ba3\u8a00\u3055\u308c\u305f<code>var<\/code>\u306e\u30b9\u30b3\u30fc\u30d7\u306f\u3001<a href=\"https:\/\/hacks.mozilla.org\/2015\/07\/es6-in-depth-let-and-const\/\" target=\"_blank\" rel=\"noopener noreferrer\">\u305d\u306e\u95a2\u6570\u672c\u4f53\u306e\u5168\u4f53<\/a>\u3067\u3059\u3002<\/p>\n<p>\u3064\u307e\u308a\u3001\u5909\u6570\u306f\u30d6\u30ed\u30c3\u30af\u30ec\u30d9\u30eb\u3067\u306f\u306a\u304f\u3001\u95a2\u6570\u5168\u4f53\u306e\u30ec\u30d9\u30eb\u3067\u5b9a\u7fa9\u3055\u308c\u308b\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002\u3053\u308c\u306f\u3001JavaScript\u306e\u30b3\u30fc\u30c9\u306b\u30d0\u30b0\u3092\u3082\u305f\u3089\u3057\u3001\u4fdd\u5b88\u3092\u56f0\u96e3\u306b\u3059\u308b\u69d8\u3005\u306a\u554f\u984c\u3092\u5f15\u304d\u8d77\u3053\u3057\u307e\u3059\u3002<\/p>\n<p>\u305d\u3093\u306a\u554f\u984c\u3092\u89e3\u6c7a\u3059\u308b\u305f\u3081\u306b\u3001ES6\u3067\u306f<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/let\" target=\"_blank\" rel=\"noopener noreferrer\"><code>let<\/code><\/a>\u304c\u5c0e\u5165\u3055\u308c\u307e\u3057\u305f\u3002<\/p>\n<blockquote><p><code>let<\/code>\u306e\u5ba3\u8a00\u306f\u3001<strong>\u30d6\u30ed\u30c3\u30af\u30b9\u30b3\u30fc\u30d7<\/strong>\u306e\u30ed\u30fc\u30ab\u30eb\u5909\u6570\u3092\u5ba3\u8a00\u3057\u3001\u30aa\u30d7\u30b7\u30e7\u30f3\u3067\u305d\u308c\u3092\u5024\u306b\u521d\u671f\u5316<span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">\u3057\u307e<\/span><span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">\u3059\u3002<\/span><\/p><\/blockquote>\n<p><code>let<\/code>\u304c<code>var<\/code>\u3088\u308a\u3082\u512a\u308c\u3066\u3044\u308b\u70b9\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n<ul>\n<li><strong><code>let<\/code>\u306f\u30d6\u30ed\u30c3\u30af\u6587\u306e\u30b9\u30b3\u30fc\u30d7\u306b\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u3082\u306e\u3067\u3059<\/strong>\u3002\u4e00\u65b9\u3067<code>var<\/code>\u306f\u3001\u30d6\u30ed\u30c3\u30af\u30b9\u30b3\u30fc\u30d7\u306b\u95a2\u4fc2\u306a\u304f\u3001\u95a2\u6570\u5168\u4f53\u306b\u5bfe\u3057\u3066\u30b0\u30ed\u30fc\u30d0\u30eb\u307e\u305f\u306f\u30ed\u30fc\u30ab\u30eb\u306b\u5909\u6570\u3092\u5ba3\u8a00\u3057\u307e\u3059\u3002<\/li>\n<li><strong>\u30b0\u30ed\u30fc\u30d0\u30eb\u5909\u6570<code>let<\/code>\u306f\u3001<code>window<\/code>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3067\u306f\u3042\u308a\u307e\u305b\u3093<\/strong>\u3002<code>window.variableName<\/code>\u3067\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002<\/li>\n<li><strong><code>let<\/code>\u306f\u3001\u305d\u306e\u5ba3\u8a00\u306b\u9054\u3057\u305f\u5f8c\u306b\u306e\u307f\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059<\/strong>\u3002\u5909\u6570\u306f\u3001\u5236\u5fa1\u30d5\u30ed\u30fc\u304c\u5ba3\u8a00\u3055\u308c\u305f\u30b3\u30fc\u30c9\u884c\u306b\u5230\u9054\u3059\u308b\u307e\u3067\u521d\u671f\u5316\u3055\u308c\u307e\u305b\u3093\uff08let\u306e\u5ba3\u8a00\u306f<strong>\u975e\u30db\u30a4\u30b9\u30c8<\/strong>\u3067\u3059\uff09\u3002<\/li>\n<li><strong><code>let<\/code>\u3067\u5909\u6570\u3092\u518d\u5ba3\u8a00\u3059\u308b\u3068\u3001<code>SyntaxError<\/code> \u3092\u6295\u3052\u307e\u3059\u3002<\/strong><\/li>\n<\/ul>\n<p><code>var<\/code>\u3092\u4f7f\u3063\u3066\u5ba3\u8a00\u3057\u305f\u5909\u6570\u306f\u30d6\u30ed\u30c3\u30af\u30b9\u30b3\u30fc\u30d7\u3092\u4f5c\u3089\u306a\u3044\u305f\u3081\u3001\u30eb\u30fc\u30d7\u5185\u3084<code>if<\/code>\u6587\u306e\u5185\u90e8\u3067<code>var<\/code>\u3092\u4f7f\u3063\u3066\u5909\u6570\u3092\u5b9a\u7fa9\u3059\u308b\u3068\u3001\u30d6\u30ed\u30c3\u30af\u5916\u304b\u3089\u30a2\u30af\u30bb\u30b9\u3057\u3066\u3057\u307e\u3046\u53ef\u80fd\u6027\u304c\u3042\u308a\u3001\u30b3\u30fc\u30c9\u306e\u30d0\u30b0\u306b\u3064\u306a\u304c\u308b\u3053\u3068\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u6700\u521d\u306e\u4f8b\u306e\u30b3\u30fc\u30c9\u306f\u3001\u30a8\u30e9\u30fc\u306a\u304f\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002\u3067\u306f\u3001\u4e0a\u3067\u898b\u305f\u30b3\u30fc\u30c9\u306e\u30d6\u30ed\u30c3\u30af\u306e<code>var<\/code>\u3092<code>let<\/code>\u306b\u7f6e\u304d\u63db\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-js\">console.log(msg);\nlet msg = \"Hello!\";\nconsole.log(msg);<\/code><\/pre>\n<p>2\u756a\u76ee\u306e\u4f8b\u3067\u306f\u3001<code>var<\/code>\u306e\u4ee3\u308f\u308a\u306b<code>let<\/code>\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001<code>Uncaught ReferenceError<\/code>\u304c\u751f\u6210\u3055\u308c\u307e\u3059\u3002<\/p>\n<figure id=\"attachment_151741\" aria-describedby=\"caption-attachment-151741\" style=\"width: 1176px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-151741\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-referenceerror.jpg\" alt=\"Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable \uff09\" width=\"1176\" height=\"222\"><figcaption id=\"caption-attachment-151741\" class=\"wp-caption-text\">Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable \uff09<\/figcaption><\/figure>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u3057\u305f\u304c\u3063\u3066\u3001\u4e00\u822c\u7684\u306a\u30eb\u30fc\u30eb\u3068\u3057\u3066\u3001<code>var<\/code>\u306e\u4ee3\u308f\u308a\u306b<code>let<\/code>\u3092\u5e38\u306b\u4f7f\u7528<\/strong>\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<\/aside>\n\n<p>ES6\u3067\u306f\u30013\u3064\u76ee\u3068\u3057\u3066<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/const\"><code>const<\/code><\/a>\u3082\u5c0e\u5165\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p><code>const<\/code>\u306f\u3001<code>let<\/code>\u3068\u3088\u304f\u4f3c\u3066\u3044\u307e\u3059\u304c\u3001\u91cd\u8981\u306a\u9055\u3044\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f <code>const<\/code>\u3067\u5ba3\u8a00\u3055\u308c\u305f\u5909\u6570\u306f\u3001\u5ba3\u8a00\u3055\u308c\u305f\u6642\u70b9\u4ee5\u5916\u3067\u306f\u5024\u3092\u4ee3\u5165\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u305b\u3093\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u6b21\u306e\u3088\u3046\u306a\u4f8b\u3092\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-js\">const MAX_VALUE = 1000;\nMAX_VALUE = 2000;<\/code><\/pre>\n<p>\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a<a href=\"https:\/\/kinsta.com\/jp\/blog\/errors-in-javascript\/#typeerror\">TypeError<\/a>\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<figure id=\"attachment_151743\" aria-describedby=\"caption-attachment-151743\" style=\"width: 1012px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151743 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-assignment-to-constant-variable.jpg\" alt=\"Google Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable\uff09\" width=\"1012\" height=\"268\"><figcaption id=\"caption-attachment-151743\" class=\"wp-caption-text\">Google Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable\uff09<\/figcaption><\/figure>\n<p>\u3055\u3089\u306b\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u5024\u3092\u4e0e\u3048\u305a\u306b<code>const<\/code>\u3092\u5ba3\u8a00\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u5024\u3092\u4e0e\u3048\u305a\u306b<code>const<\/code>\u3092\u5ba3\u8a00\u3059\u308b\u3068\u3001\u6b21\u306e<code>SyntaxError<\/code>\u304c\u6295\u3052\u3089\u308c\u307e\u3059\uff08<a href=\"https:\/\/hacks.mozilla.org\/2015\/07\/es6-in-depth-let-and-const\/\">ES6 In Depth: let\u3068const<\/a>\u3082\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\uff09\u3002<\/p>\n<figure id=\"attachment_151746\" aria-describedby=\"caption-attachment-151746\" style=\"width: 1200px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151746 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-syntax-error-missing-initializer-in-const-declaration.jpg\" alt=\"Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught SyntaxError: Missing initializer in const declaration\uff09\" width=\"1200\" height=\"214\"><figcaption id=\"caption-attachment-151746\" class=\"wp-caption-text\">Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught SyntaxError: Missing initializer in const declaration\uff09<\/figcaption><\/figure>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u5b9a\u6570\u306f\u518d\u5ba3\u8a00\u3067\u304d\u305a\u3001\u518d\u5272\u308a\u5f53\u3066\u306b\u3088\u3063\u3066\u5024\u3092\u5909\u66f4\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u305b\u3093\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u3057\u304b\u3057\u3001\u5b9a\u6570\u304c\u914d\u5217\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3067\u3042\u308b\u5834\u5408\u3001\u305d\u306e\u914d\u5217\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u5185\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3084\u9805\u76ee\u3092\u8abf\u6574\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>\u4f8b\u3048\u3070\u3001\u914d\u5217\u306e\u9805\u76ee\u3092\u5909\u66f4\u3057\u305f\u308a\u3001\u8ffd\u52a0\u3057\u305f\u308a\u3001\u524a\u9664\u3057\u305f\u308a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Declare a constant array\nconst cities = [\"London\", \"New York\", \"Sydney\"];\n\n\/\/ Change an item\ncities[0] = \"Madrid\";\n\n\/\/ Add an item\ncities.push(\"Paris\");\n\n\/\/ Remove an item\ncities.pop();\n\nconsole.log(cities);\n\n\/\/ Array(3)\n\/\/ 0: \"Madrid\"\n\/\/ 1: \"New York\"\n\/\/ 2: \"Sydney\"<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001\u914d\u5217\u3092\u518d\u5272\u308a\u5f53\u3066\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002<\/p>\n<pre><code class=\"language-js\">const cities = [\"London\", \"New York\", \"Sydney\"];\n\ncities = [\"Athens\", \"Barcelona\", \"Naples\"];<\/code><\/pre>\n<p>\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/TypeError\" target=\"_blank\" rel=\"noopener noreferrer\">TypeError<\/a>\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<figure id=\"attachment_151747\" aria-describedby=\"caption-attachment-151747\" style=\"width: 1166px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151747 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-uncaught-type-error-assignment-to-constant-variable-2.jpg\" alt=\"Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable\uff09\" width=\"1166\" height=\"227\"><figcaption id=\"caption-attachment-151747\" class=\"wp-caption-text\">Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Assignment to constant variable\uff09<\/figcaption><\/figure>\n<p>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3084\u30e1\u30bd\u30c3\u30c9\u3082\u8ffd\u52a0\u3001\u518d\u5272\u308a\u5f53\u3066\u3001\u524a\u9664\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Declare a constant obj\nconst post = {\n\tid: 1,\n\tname: 'JavaScript is awesome',\n\texcerpt: 'JavaScript is an awesome scripting language',\n\tcontent: 'JavaScript is a scripting language that enables you to create dynamically updating content.'\n};\n\n\/\/ add a new property\npost.slug = \"javascript-is-awesome\";\n\n\/\/ Reassign property\npost.id = 5;\n\n\/\/ Delete a property\ndelete post.excerpt;\n\nconsole.log(post);\n\n\/\/ {id: 5, name: 'JavaScript is awesome', content: 'JavaScript is a scripting language that enables you to create dynamically updating content.', slug: 'javascript-is-awesome'}<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u305d\u306e\u3082\u306e\u3092\u518d\u5272\u308a\u5f53\u3066\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002\u6b21\u306e\u30b3\u30fc\u30c9\u306f\u3001<code>Uncaught TypeError<\/code>\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Declare a constant obj\nconst post = {\n\tid: 1,\n\tname: 'JavaScript is awesome',\n\texcerpt: 'JavaScript is an awesome scripting language'\n};\n\npost = {\n\tid: 1,\n\tname: 'React is powerful',\n\texcerpt: 'React lets you build user interfaces'\n};<\/code><\/pre>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f React\u3067\u306f\u3001<code>const<\/code>\u3067\u5909\u6570\u3092\u5ba3\u8a00\u3059\u308b\u306e\u304c\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u3059\u3002<code>let<\/code>\u306f\u3001<code>const<\/code>\u304c\u9069\u5207\u3067\u306a\u3044\u5834\u5408\u306b\u4f7f\u7528\u3057\u307e\u3059\u3002<code>var<\/code>\u306e\u4f7f\u7528\u306f\u63a8\u5968\u3055\u308c\u307e\u305b\u3093\u3002<\/strong><\/p>\n<\/aside>\n\n<h3>Object.freeze()<\/h3>\n<p><code>const<\/code>\u3092\u4f7f\u3063\u3066\u3082\u3001\u5fc5\u305a\u3057\u3082\u5f37\u529b\u306a\u4e0d\u5909\u6027\u304c\u4fdd\u8a3c\u3055\u308c\u308b\u308f\u3051\u3067\u306f\u306a\u3044\uff08\u7279\u306b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3084\u914d\u5217\u3092\u6271\u3046\u5834\u5408\uff09\u3053\u3068\u306f\u3001\u3053\u3053\u307e\u3067\u306e\u8aac\u660e\u3067\u7406\u89e3\u3067\u304d\u305f\u3068\u601d\u3044\u307e\u3059\u3002\u3067\u306f\u3001React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3067\u4e0d\u5909\u6027\u306e\u30d1\u30bf\u30fc\u30f3\u3092\u5b9f\u88c5\u3059\u308b\u306b\u306f\u3069\u3046\u3059\u308c\u3070\u3088\u3044\u306e\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n<p>\u307e\u305a\u3001\u914d\u5217\u306e\u8981\u7d20\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u5909\u66f4\u3055\u308c\u308b\u306e\u3092\u9632\u304e\u305f\u3044\u3068\u304d\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Object\/freeze\" target=\"_blank\" rel=\"noopener noreferrer\">\u9759\u7684\u30e1\u30bd\u30c3\u30c9<code>Object.freeze()<\/code><\/a> \u3092\u4f7f\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n<blockquote><p>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u51cd\u7d50\u3059\u308b\u3068\u3001\u62e1\u5f35\u304c\u3067\u304d\u306a\u304f\u306a\u308a\u3001\u65e2\u5b58\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u66f8\u304d\u8fbc\u307f\u4e0d\u53ef\u3001\u8a2d\u5b9a\u4e0d\u53ef\u306b\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u65b0\u3057\u3044\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u8ffd\u52a0\u3057\u305f\u308a\u3001\u65e2\u5b58\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u524a\u9664\u3057\u305f\u308a\u3001\u5217\u6319\u53ef\u80fd\u6027\u3001\u8a2d\u5b9a\u53ef\u80fd\u6027\u3001\u66f8\u304d\u8fbc\u307f\u53ef\u80fd\u6027\u3001\u5024\u3092\u5909\u66f4\u3057\u305f\u308a\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u3092\u518d\u5272\u308a\u5f53\u3066\u3059\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u305b\u3093\u3002<code>freeze()<\/code>\u306f\u6e21\u3055\u308c\u305f\u3082\u306e\u3068\u540c\u3058\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p><\/blockquote>\n<p>\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u8ffd\u52a0\u3001\u5909\u66f4\u3001\u524a\u9664\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001<code>TypeError<\/code>\u3092\u6295\u3052\u3066\uff08\u307e\u305f\u306f\u305d\u308c\u304c\u660e\u793a\u3055\u308c\u308b\u3053\u3068\u306a\u304f\uff09\u51e6\u7406\u304c\u5931\u6557\u3057\u307e\u3059\u3002\u3053\u308c\u306f\u3001\u7279\u306b<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Strict_mode\">strict\uff08\u53b3\u683c\uff09\u30e2\u30fc\u30c9<\/a>\u3067\u3088\u304f\u898b\u3089\u308c\u308b\u4e8b\u8c61\u3067\u3059\u3002<\/p>\n<p><code>Object.freeze()<\/code>\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">'use strict'\n\/\/ Declare a constant obj\nconst post = {\n\tid: 1,\n\tname: 'JavaScript is awesome',\n\texcerpt: 'JavaScript is an awesome scripting language'\n};\n\/\/ Freeze the object\nObject.freeze(post);<\/code><\/pre>\n<p>\u305d\u3057\u3066\u3001\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u8ffd\u52a0\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001<code>Uncaught TypeError<\/code>\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Add a new property\npost.slug = \"javascript-is-awesome\"; \/\/ Uncaught TypeError<\/code><\/pre>\n<figure id=\"attachment_151753\" aria-describedby=\"caption-attachment-151753\" style=\"width: 1256px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151753 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-object-is-not-extensible.jpg\" alt=\"Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: can\u2019t define property \u201cslug\u201d: Object is not extensible \uff09\" width=\"1256\" height=\"300\"><figcaption id=\"caption-attachment-151753\" class=\"wp-caption-text\">Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: can\u2019t define property \u201cslug\u201d: Object is not extensible \uff09<\/figcaption><\/figure>\n<p>\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u518d\u5272\u308a\u5f53\u3066\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001\u5225\u306e\u7a2e\u985e\u306e<code>TypeError<\/code>\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Reassign property\npost.id = 5; \/\/ Uncaught TypeError<\/code><\/pre>\n<figure id=\"attachment_151865\" aria-describedby=\"caption-attachment-151865\" style=\"width: 1198px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151865 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-read-only-property.jpg\" alt=\"\u8aad\u307f\u53d6\u308a\u5c02\u7528\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u518d\u5272\u308a\u5f53\u3066\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3059\u308b\" width=\"1198\" height=\"288\"><figcaption id=\"caption-attachment-151865\" class=\"wp-caption-text\">\u8aad\u307f\u53d6\u308a\u5c02\u7528\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u518d\u5272\u308a\u5f53\u3066\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u30a8\u30e9\u30fc\u304c\u767a\u751f\u3059\u308b<\/figcaption><\/figure>\n<figure id=\"attachment_151868\" aria-describedby=\"caption-attachment-151868\" style=\"width: 1190px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151868 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-cannot-assign-to-read-only-property.jpg\" alt=\"Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Cannot assign to read only property \u2018id\u2019 of object \u2018#&lt;Object&gt;\u2019 \uff09\" width=\"1190\" height=\"254\"><figcaption id=\"caption-attachment-151868\" class=\"wp-caption-text\">Chrome\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: Cannot assign to read only property \u2018id\u2019 of object \u2018#&lt;Object&gt;\u2019 \uff09<\/figcaption><\/figure>\n<p>\u307e\u305f\u3001\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u524a\u9664\u3057\u3088\u3046\u3068\u3057\u3066\u3082\u540c\u3058\u3067\u3059\u3002\u7d50\u679c\u306f\u3001<code>TypeError<\/code>\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">\/\/ Delete a property\ndelete post.excerpt; \/\/ Uncaught TypeError<\/code><\/pre>\n<figure id=\"attachment_151869\" aria-describedby=\"caption-attachment-151869\" style=\"width: 1370px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151869 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/uncaught-type-error-property-excerpt-is-non-configurable-and-cant-be-deleted-firefox.jpg\" alt=\"Firefox\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: property \u201cexcerpt\u201d is non-configurable and can\u2019t be deleted\uff09\" width=\"1370\" height=\"298\"><figcaption id=\"caption-attachment-151869\" class=\"wp-caption-text\">Firefox\u306e\u30a8\u30e9\u30fc\uff08Uncaught TypeError: property \u201cexcerpt\u201d is non-configurable and can\u2019t be deleted\uff09<\/figcaption><\/figure>\n<h2>\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb<\/h2>\n<p>JavaScript\u3067\u6587\u5b57\u5217\u3068\u5f0f\u306e\u51fa\u529b\u3092\u7d50\u5408\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b\u5834\u5408\u3001\u901a\u5e38\u306f\u52a0\u7b97\u6f14\u7b97\u5b50<code>+<\/code>\u3092\u4f7f\u7528\u3057\u307e\u3059\u3002\u3057\u304b\u3057\u3001\u52a0\u7b97\u6f14\u7b97\u5b50\u3092\u4f7f\u308f\u305a\u306b\u6587\u5b57\u5217\u306e\u4e2d\u306b\u5f0f\u3092\u542b\u3081\u308b\u6a5f\u80fd\u3082\u3042\u308a\u307e\u3059\u3002\u305d\u308c\u304c\u3001<strong>\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb<\/strong>\u3067\u3059\u3002<\/p>\n<p><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Template_literals\" target=\"_blank\" rel=\"noopener noreferrer\">\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb<\/a>\u306f\u3001\u30d0\u30c3\u30af\u30af\u30aa\u30fc\u30c8\uff08<code>`<\/code>\uff09\u3067\u533a\u5207\u3089\u308c\u305f\u7279\u6b8a\u306a\u6587\u5b57\u5217\u3067\u3059\u3002<\/p>\n<p>\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306b\u306f\u3001\u30d7\u30ec\u30fc\u30b9\u30db\u30eb\u30c0\u30fc\u3092\u542b\u3081\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u30d7\u30ec\u30fc\u30b9\u30db\u30eb\u30c0\u30fc\u306b\u306f\u3001\u30c9\u30eb\u6587\u5b57\u3068\u4e2d\u62ec\u5f27\u3092\u4f7f\u7528\u3057\u307e\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306f\u305d\u306e\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const align = 'left';\nconsole.log(`This string is ${ align }-aligned`);<\/code><\/pre>\n<p>\u6587\u5b57\u5217\u3068\u30d7\u30ec\u30fc\u30b9\u30db\u30eb\u30c0\u30fc\u304c\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u95a2\u6570\u306b\u6e21\u3055\u308c\u3001\u305d\u3053\u3067\u6587\u5b57\u5217\u306e\u88dc\u9593\u51e6\u7406\u306b\u3088\u308a\u7f6e\u304d\u63db\u3048\u304c\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002\u305d\u3057\u3066\u3001\u6700\u7d42\u7684\u306b\u306f\u9023\u7d50\u3057\u305f1\u3064\u306e\u6587\u5b57\u5217\u306b\u306a\u308a\u307e\u3059\u3002\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u95a2\u6570\u3092\u72ec\u81ea\u306e\u95a2\u6570\u306b\u7f6e\u304d\u63db\u3048\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306f\u3001\u4ee5\u4e0b\u306e\u7528\u9014\u306b\u4f7f\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><strong>\u8907\u6570\u884c\u306e\u6587\u5b57\u5217<\/strong>\uff1a\u6539\u884c\u6587\u5b57\u304c\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306b\u53cd\u6620\u3055\u308c\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">console.log(`Twinkle, twinkle, little bat!\nHow I wonder what you\u2019re at!`);<\/code><\/pre>\n<p><strong>\u6587\u5b57\u5217\u306e\u88dc\u9593<\/strong>\uff1a\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306a\u3057\u3067\u306f\u3001\u5f0f\u306e\u51fa\u529b\u3092\u6587\u5b57\u5217\u3068\u7d50\u5408\u3059\u308b\u305f\u3081\u306b\u52a0\u7b97\u6f14\u7b97\u5b50\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002\u6b21\u306e\u4f8b\u3092\u3054\u89a7\u304f\u3060\u3055\u3044\u3002<\/p>\n<pre><code class=\"language-js\">const a = 3;\nconst b = 7;\nconsole.log(\"The result of \" + a + \" + \" + b + \" is \" + (a + b));<\/code><\/pre>\n<p>\u3061\u3087\u3063\u3068\u308f\u304b\u308a\u306b\u304f\u3044\u5370\u8c61\u3092\u53d7\u3051\u307e\u3059\u3002\u305d\u3053\u3067\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u3092\u4f7f\u3048\u3070\u3001\u3053\u306e\u30b3\u30fc\u30c9\u3092\u3082\u3063\u3068\u8aad\u307f\u3084\u3059\u304f\u3001\u30e1\u30f3\u30c6\u30ca\u30f3\u30b9\u3057\u3084\u3059\u3044\u65b9\u6cd5\u3067\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const a = 3;\nconst b = 7;\nconsole.log(`The result of ${ a } + ${ b } is ${ a + b }`);<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001\u3053\u306e<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Template_literals#string_interpolation\" target=\"_blank\" rel=\"noopener noreferrer\">2\u3064\u306e\u69cb\u6587\u306b\u306f\u9055\u3044<\/a>\u304c\u3042\u308b\u3053\u3068\u306b\u7559\u610f\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306f\u5f0f\u3092\u76f4\u63a5\u6587\u5b57\u5217\u306b\u5f37\u5236\u3059\u308b\u306e\u306b\u5bfe\u3057\u3001\u52a0\u7b97\u306f\u88ab\u6f14\u7b97\u5b50\u3092\u307e\u305a\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u306b\u5f37\u5236\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306f\u3001\u3044\u304f\u3064\u304b\u306e\u7528\u9014\u306b\u9069\u3057\u3066\u3044\u307e\u3059\u3002\u6b21\u306e\u4f8b\u3067\u306f\u3001<a href=\"#ternary-operator\" target=\"_blank\" rel=\"noopener noreferrer\">\u4e09\u9805\u6f14\u7b97\u5b50<\/a>\u3092\u4f7f\u7528\u3057\u3066\u3001<code>class<\/code>\u5c5e\u6027\u306b\u5024\u3092\u5272\u308a\u5f53\u3066\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const page = 'archive';\nconsole.log(`class=${ page === 'archive' <code>?<\/code> 'archive' : 'single' }`);<\/code><\/pre>\n<p>\u4ee5\u4e0b\u3067\u306f\u3001\u7c21\u5358\u306a\u8a08\u7b97\u3092\u884c\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const price = 100;\nconst VAT = 0.22;\n\nconsole.log(`Total price: ${ (price * (1 + VAT)).toFixed(2) }`);<\/code><\/pre>\n<p>\u307e\u305f\u3001<code>${expression}<\/code>\u30d7\u30ec\u30fc\u30b9\u30db\u30eb\u30c0\u30fc\u306e\u4e2d\u306b\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u3092\u5165\u308c\u3066\u30cd\u30b9\u30c8\u3059\u308b\u3053\u3068\u3082\u53ef\u80fd\u3067\u3059\uff08\u305f\u3060\u3057\u3001\u8907\u96d1\u306a\u6587\u5b57\u5217\u69cb\u9020\u306f\u8aad\u307f\u53d6\u308a\u3084\u4fdd\u5b88\u304c\u56f0\u96e3\u306b\u306a\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u305f\u3081\u3001<a href=\"https:\/\/dev.to\/remrkabledev\/nesting-template-literals-a-recommended-approach-2jgj\" target=\"_blank\" rel=\"noopener noreferrer\">\u30cd\u30b9\u30c8\u3057\u305f\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306e\u4f7f\u7528\u306f\u614e\u91cd\u306b<\/a>\uff09\u3002<\/p>\n<p><strong>\u30bf\u30b0\u4ed8\u304d\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8<\/strong>\uff1a\u524d\u8ff0\u306e\u3088\u3046\u306b\u3001\u6587\u5b57\u5217\u306e\u9023\u7d50\u3092\u884c\u3046\u72ec\u81ea\u306e\u95a2\u6570\u3092\u5b9a\u7fa9\u3059\u308b\u3053\u3068\u3082\u53ef\u80fd\u3067\u3059\u3002\u3053\u306e\u3088\u3046\u306a\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u3092<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Template_literals#tagged_templates\" target=\"_blank\" rel=\"noopener noreferrer\">\u30bf\u30b0\u4ed8\u304d\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8<\/a>\u3068\u547c\u3073\u307e\u3059\u3002<\/p>\n<blockquote><p>\u30bf\u30b0\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u3092\u95a2\u6570\u3067\u89e3\u6790\u3067\u304d\u307e\u3059\u3002\u30bf\u30b0\u95a2\u6570\u306e\u6700\u521d\u306e\u5f15\u6570\u306b\u306f\u3001\u6587\u5b57\u5217\u30ea\u30c6\u30e9\u30eb\u306e\u914d\u5217\u3092\u542b\u307f\u307e\u3059\u3002\u6b8b\u308a\u306e\u5f15\u6570\u306f\u5f0f\u306b\u95a2\u9023\u4ed8\u3051\u3089\u308c\u307e\u3059\u3002<\/p><\/blockquote>\n<p>\u30bf\u30b0\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u72ec\u81ea\u306e\u95a2\u6570\u3067\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u3092\u89e3\u6790\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u3053\u306e\u95a2\u6570\u306e\u7b2c\u4e00\u5f15\u6570\u306b\u306f\u3001\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb\u306b\u542b\u307e\u308c\u308b\u6587\u5b57\u5217\u306e\u914d\u5217\u304c\u3001\u4ed6\u306e\u5f15\u6570\u306b\u306f\u5f0f\u304c\u5165\u308a\u307e\u3059\u3002<\/p>\n<p>\u72ec\u81ea\u306e\u95a2\u6570\u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u3067\u3001\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u306e\u5f15\u6570\u306b\u5bfe\u3057\u3066\u4efb\u610f\u306e\u64cd\u4f5c\u3092\u884c\u3044\u3001\u64cd\u4f5c\u3055\u308c\u305f\u6587\u5b57\u5217\u3092\u8fd4\u3059\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u4ee5\u4e0b\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Template_literals#tagged_templates\" target=\"_blank\" rel=\"noopener noreferrer\">\u30bf\u30b0\u4ed8\u304d\u30c6\u30f3\u30d7\u30ec\u30fc\u30c8\u30ea\u30c6\u30e9\u30eb<\/a>\u306e\u3054\u304f\u57fa\u672c\u7684\u306a\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-js\">const name = \"Carlo\";\nconst role = \"student\";\nconst organization = \"North Pole University\";\nconst age = 25;\n\nfunction customFunc(strings, ...tags) {\n\tconsole.log(strings); \/\/ ['My name is ', \", I'm \", ', and I am ', ' at ', '', raw: Array(5)]\n\tconsole.log(tags); \/\/ ['Carlo', 25, 'student', 'North Pole University']\n\tlet string = '';\n\tfor ( let i = 0; i &lt; strings.length - 1; i++ ){\n\t\tconsole.log(i + \"\" + strings[i] + \"\" + tags[i]);\n\t\tstring += strings[i] + tags[i];\n\t}\n\treturn string.toUpperCase();\n}\n\nconst output = customFunc`My name is ${name}, I'm ${age}, and I am ${role} at ${organization}`;\nconsole.log(output);<\/code><\/pre>\n<p>\u4e0a\u306e\u30b3\u30fc\u30c9\u306f\u3001<code>strings<\/code>\u3068<code>tags<\/code>\u306e\u914d\u5217\u8981\u7d20\u3092\u8868\u793a\u3057\u3001\u6587\u5b57\u5217\u3092\u5927\u6587\u5b57\u306b\u3057\u3066\u304b\u3089\u30d6\u30e9\u30a6\u30b6\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u51fa\u529b\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<h2>\u30a2\u30ed\u30fc\u95a2\u6570<\/h2>\n<p>\u30a2\u30ed\u30fc\u95a2\u6570\u306f\u3001JavaScript\u306e\u7121\u540d\u95a2\u6570\uff08\u540d\u524d\u306e\u306a\u3044\u95a2\u6570\uff09\u306b\u4ee3\u308f\u308b\u3082\u306e\u3067\u3059\u304c\u3001\u3044\u304f\u3064\u304b\u306e\u9055\u3044\u3084\u5236\u9650\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u4ee5\u4e0b\u306e\u5ba3\u8a00\u306f\u3001\u3059\u3079\u3066\u6709\u52b9\u306a\u30a2\u30ed\u30fc\u95a2\u6570\u306e\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">\/\/ Arrow function without parameters\nconst myFunction = () =&gt; expression;\n\n\/\/ Arrow function with one parameter\nconst myFunction = param =&gt; expression;\n\n\/\/ Arrow function with one parameter\nconst myFunction = (param) =&gt; expression;\n\n\/\/ Arrow function with more parameters\nconst myFunction = (param1, param2) =&gt; expression;\n\n\/\/ Arrow function without parameters\nconst myFunction = () =&gt; {\n\tstatements\n}\n\n\/\/ Arrow function with one parameter\nconst myFunction = param =&gt; {\n\tstatements\n}\n\n\/\/ Arrow function with more parameters\nconst myFunction = (param1, param2) =&gt; {\n\tstatements\n}<\/code><\/pre>\n<p>\u95a2\u6570\u306b\u6e21\u3059\u30d1\u30e9\u30e1\u30fc\u30bf\u304c1\u3064\u3060\u3051\u306e\u5834\u5408\u306f\u3001\u4e38\u62ec\u5f27\u3092\u7701\u7565\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u30022\u3064\u4ee5\u4e0a\u306e\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u6e21\u3059\u5834\u5408\u306f\u3001\u62ec\u5f27\u3067\u56f2\u3080\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002\u4ee5\u4e0b\u306f\u305d\u306e\u4f8b\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const render = ( id, title, category ) =&gt; `${id}: ${title} - ${category}`;\nconsole.log( render ( 5, 'Hello World!', \"JavaScript\" ) );<\/code><\/pre>\n<p>\u4e00\u884c\u306e\u30a2\u30ed\u30fc\u95a2\u6570\u306f\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002\u8907\u6570\u884c\u306e\u69cb\u6587\u3092\u4f7f\u7528\u3059\u308b\u5834\u5408\u306f\u3001\u624b\u52d5\u3067\u5024\u3092\u8fd4\u3059\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const render = ( id, title, category ) =&gt; {\n\tconsole.log( `Post title: ${ title }` );\n\treturn `${ id }: ${ title } - ${ category }`;\n}\nconsole.log( `Post details: ${ render ( 5, 'Hello World!', \"JavaScript\" ) }` );<\/code><\/pre>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3067\u306f\u3001\u4f7f\u7528\u3057\u306a\u3044\u7279\u5225\u306a\u7406\u7531\u304c\u306a\u3044\u9650\u308a\u3001\u901a\u5e38\u30a2\u30ed\u30fc\u95a2\u6570\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u901a\u5e38\u306e\u95a2\u6570\u3068\u30a2\u30ed\u30fc\u95a2\u6570\u306e\u91cd\u8981\u306a\u9055\u3044\u3068\u3057\u3066\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u306f<code>this<\/code>\u306b\u5bfe\u3059\u308b\u72ec\u81ea\u306e\u30d0\u30a4\u30f3\u30c7\u30a3\u30f3\u30b0\u3092\u6301\u3061\u307e\u305b\u3093\u3002\u30a2\u30ed\u30fc\u95a2\u6570\u3067<code>this<\/code>\u3092\u4f7f\u7528\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001\u95a2\u6570\u30b9\u30b3\u30fc\u30d7\u5916\u306b\u51fa\u3066\u3057\u307e\u3044\u307e\u3059\u3002<\/p>\n<p>\u30a2\u30ed\u30fc\u95a2\u6570\u306e\u8a73\u7d30\u306a\u8aac\u660e\u3068\u4f7f\u7528\u4f8b\u306b\u3064\u3044\u3066\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Functions\/Arrow_functions\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u3082\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<h2>\u30af\u30e9\u30b9<\/h2>\n<p><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Learn\/JavaScript\/Objects\/Classes_in_JavaScript\" target=\"_blank\" rel=\"noopener noreferrer\">JavaScript\u306e\u30af\u30e9\u30b9<\/a>\u306f\u8a2d\u8a08\u56f3\u306e\u3088\u3046\u306a\u3082\u306e\u3067\u3042\u308a\u3001\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u306e\u7d99\u627f\u30e1\u30ab\u30cb\u30ba\u30e0\u3092\u4f7f\u7528\u3059\u308b\uff08\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304b\u3089\u7d99\u627f\u3059\u308b\uff09\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\/\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<p><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Inheritance_and_the_prototype_chain\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u306b\u3088\u308b\u3068\u3001\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n<blockquote><p>\u7d99\u627f\u306b\u95a2\u3057\u3066\u8a00\u3048\u3070\u3001JavaScript\u306b\u306f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3068\u3044\u30461\u3064\u306e\u69cb\u6210\u8981\u7d20\u304c\u3042\u308b\u3060\u3051\u3067\u3059\u3002\u5404\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306f\u3001\u305d\u306e\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u3068\u547c\u3070\u308c\u308b\u5225\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3078\u306e\u30ea\u30f3\u30af\u3092\u4fdd\u6301\u3057\u307e\u3059\u3002\u305d\u306e\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306f\u3001\u305d\u308c\u81ea\u8eab\u306e\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u3092\u6301\u3061\u3001<code>null<\/code>\u3092\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u3068\u3059\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u5230\u9054\u3059\u308b\u307e\u3067\u3001\u305d\u306e\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u6301\u3064\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002<\/p><\/blockquote>\n<p>\u95a2\u6570\u3068\u540c\u69d8\u306b\u3001\u30af\u30e9\u30b9\u3092\u5b9a\u7fa9\u3059\u308b\u65b9\u6cd5\u306f2\u3064\u3042\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\u30af\u30e9\u30b9\u5f0f<\/li>\n<li>\u30af\u30e9\u30b9\u5ba3\u8a00<\/li>\n<\/ul>\n<p>\u6b21\u306e\u4f8b\u306e\u3088\u3046\u306b\u3001<code>class<\/code>\u3092\u4f7f\u7528\u3057\u3066\u3001\u5f0f\u306e\u4e2d\u3067\u30af\u30e9\u30b9\u3092\u5b9a\u7fa9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const Circle = class {\n\tconstructor(radius) {\n\t\tthis.radius = Number(radius);\n\t}\n\tarea() {\n\t\treturn Math.PI * Math.pow(this.radius, 2);\n\t}\n\tcircumference() {\n\t\treturn Math.PI * this.radius * 2;\n\t}\n}\nconsole.log('Circumference: ' + new Circle(10).circumference()); \/\/ 62.83185307179586\nconsole.log('Area: ' + new Circle(10).area()); \/\/ 314.1592653589793<\/code><\/pre>\n<p>\u30af\u30e9\u30b9\u306b\u306f\u30dc\u30c7\u30a3\uff08\u4e2d\u62ec\u5f27\u5185\u306e\u30b3\u30fc\u30c9\uff09\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u3053\u3067\u306f\u3001\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u3084\u30e1\u30bd\u30c3\u30c9\uff08\u30af\u30e9\u30b9\u30e1\u30f3\u30d0\u30fc\u3068\u3082\u547c\u3070\u308c\u308b\uff09\u3092\u5b9a\u7fa9\u3057\u307e\u3059\u3002\u30af\u30e9\u30b9\u306e\u30dc\u30c7\u30a3\u306f\u3001<code>'strict mode'<\/code>\u30c7\u30a3\u30ec\u30af\u30c6\u30a3\u30d6\u3092\u4f7f\u308f\u306a\u304f\u3068\u3082\u3001\u53b3\u683c\u30e2\u30fc\u30c9\u3067\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002<\/p>\n<p><code>constructor<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3001\u30af\u30e9\u30b9\u3067\u4f5c\u6210\u3055\u308c\u305f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u751f\u6210\u3068\u521d\u671f\u5316\u306b\u4f7f\u7528\u3055\u308c\u3001\u30af\u30e9\u30b9\u304c\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u5316\u3055\u308c\u305f\u3068\u304d\u306b\u81ea\u52d5\u7684\u306b\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002\u30af\u30e9\u30b9\u5185\u3067\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u30e1\u30bd\u30c3\u30c9\u3092\u5b9a\u7fa9\u3057\u306a\u3044\u5834\u5408\u3001JavaScript\u306f\u81ea\u52d5\u7684\u306b\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u3092\u4f7f\u7528\u3057\u307e\u3059\u3002<\/p>\n<p>\u30af\u30e9\u30b9\u306f\u3001<code>extends<\/code>\uff08\u7d99\u627f\uff09\u3092\u4f7f\u7528\u3057\u62e1\u5f35\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">class Book {\n\tconstructor(title, author) {\n\t\tthis.booktitle = title;\n\t\tthis.authorname = author;\n\t}\n\tpresent() {\n\t\treturn this.booktitle + ' is a great book from ' + this.authorname;\n\t}\n}\n\nclass BookDetails extends Book {\n\tconstructor(title, author, cat) {\n\t\tsuper(title, author);\n\t\tthis.category = cat;\n\t}\n\tshow() {\n\t\treturn this.present() + ', it is a ' + this.category + ' book';\n\t}\n}\n\nconst bookInfo = new BookDetails(\"The Fellowship of the Ring\", \"J. R. R. Tolkien\", \"Fantasy\");\nconsole.log(bookInfo.show());<\/code><\/pre>\n<p>\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u306f\u3001<code>super<\/code>\u3092\u4f7f\u7528\u3057\u3066\u3001\u89aa\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u3092\u547c\u3073\u51fa\u3059\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<code>super()<\/code>\u30e1\u30bd\u30c3\u30c9\u306b\u5f15\u6570\u3092\u6e21\u3059\u3068\u3001\u3053\u306e\u5f15\u6570\u306f\u89aa\u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u30af\u30e9\u30b9\u3067\u3082\u5229\u7528\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>JavaScript\u306e\u30af\u30e9\u30b9\u306b\u3064\u3044\u3066\u306e\u8a73\u3057\u3044\u8aac\u660e\u3084\u3001\u3044\u304f\u3064\u304b\u306e\u4f7f\u7528\u4f8b\u306b\u3064\u3044\u3066\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Classes\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u3082\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<p>\u30af\u30e9\u30b9\u306f\u3001React\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u4f5c\u6210\u3059\u308b\u306e\u306b\u3088\u304f\u4f7f\u308f\u308c\u307e\u3059\u3002\u901a\u5e38\u3001\u72ec\u81ea\u306e\u30af\u30e9\u30b9\u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u306f\u306a\u304f\u3001\u7d44\u307f\u8fbc\u307f\u306eReact\u30af\u30e9\u30b9\u3092\u62e1\u5f35\u3059\u308b\u3053\u3068\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p><a href=\"https:\/\/react.dev\/reference\/react\/Component#defining-a-class-component\" target=\"_blank\" rel=\"noopener noreferrer\">React\u306e\u30af\u30e9\u30b9<\/a>\u306b\u306f\u3001React\u306e\u8981\u7d20\u3092\u8fd4\u3059<code>render()<\/code>\u30e1\u30bd\u30c3\u30c9\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">class Animal extends React.Component {\n\trender() {\n\t\treturn &lt;h2&gt;Hey, I am a {this.props.name}!&lt;\/h2&gt;;\n\t}\n}<\/code><\/pre>\n<p>\u4e0a\u306e\u4f8b\u3067\u306f\u3001<code>Animal<\/code>\u304c\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u3059\u3002<\/p>\n<ul>\n<li>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u540d\u524d\u306f\u3001\u5927\u6587\u5b57\u3067\u59cb\u307e\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/li>\n<li>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u306f\u3001<code>extends React.Component<\/code>\u304c\u5fc5\u8981\u3067\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u3001<code>React.Component<\/code>\u306e\u30e1\u30bd\u30c3\u30c9\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/li>\n<li><code>render()<\/code>\u30e1\u30bd\u30c3\u30c9\u306fHTML\u3092\u8fd4\u3059\u306e\u3067\u5fc5\u9808\u3067\u3059\u3002<\/li>\n<\/ul>\n<p>\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u4f5c\u6210\u3057\u305f\u3089\u3001\u30da\u30fc\u30b8\u4e0a\u306bHTML\u3092\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const root = ReactDOM.createRoot(document.getElementById('root'));\nconst element = &lt;Animal name=\"Rabbit\" \/&gt;;\nroot.render(element);<\/code><\/pre>\n<p>\u4e0b\u306e\u753b\u50cf\u306f\u3001\u30da\u30fc\u30b8\u4e0a\u306e\u7d50\u679c\u3092\u793a\u3057\u3066\u3044\u307e\u3059\uff08<a href=\"https:\/\/codepen.io\/carlodaniele\/pen\/LYgPvEP\">CodePen\u3067\u5b9f\u969b\u306b\u52d5\u4f5c<\/a>\u3057\u3066\u3044\u308b\u3068\u3053\u308d\u3092\u78ba\u8a8d\u53ef\u80fd\uff09\u3002<\/p>\n<figure id=\"attachment_151880\" aria-describedby=\"caption-attachment-151880\" style=\"width: 2162px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-151880 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/react-class-component.jpg\" alt=\"\u30b7\u30f3\u30d7\u30eb\u306aReact\u306e\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\" width=\"2162\" height=\"996\"><figcaption id=\"caption-attachment-151880\" class=\"wp-caption-text\">\u30b7\u30f3\u30d7\u30eb\u306aReact\u306e\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8<\/figcaption><\/figure>\n<p>\u305f\u3060\u3057\u3001<a href=\"https:\/\/react.dev\/reference\/react\/Component#migrating-a-simple-component-from-a-class-to-a-function\" target=\"_blank\" rel=\"noopener noreferrer\">React\u3067\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u4f7f\u3046\u3053\u3068\u306f\u63a8\u5968\u3055\u308c\u3066<\/a>\u304a\u3089\u305a\u3001<a href=\"https:\/\/kinsta.com\/jp\/blog\/react-best-practices\/#12-make-use-of-functional-components\">\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u95a2\u6570\u3068\u3057\u3066\u5b9a\u7fa9<\/a>\u3059\u308b\u3053\u3068\u304c\u671b\u307e\u3057\u3044\u3068\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<h2>this<\/h2>\n<p>JavaScript\u3067\u306f\u3001<code>this<\/code>\u306f\u3001\u901a\u5e38\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3001\u30af\u30e9\u30b9\u3001\u95a2\u6570\u306e\u5185\u90e8\u3067\u4f7f\u7528\u3055\u308c\u308b\u4e00\u822c\u7684\u306a\u30d7\u30ec\u30fc\u30b9\u30db\u30eb\u30c0\u30fc\u3067\u3042\u308a\u3001\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3084\u30b9\u30b3\u30fc\u30d7\u306b\u3088\u3063\u3066\u7570\u306a\u308b\u8981\u7d20\u3092\u53c2\u7167\u3057\u307e\u3059\u3002<\/p>\n<p><strong><code>this<\/code>\u306f\u3001\u30b0\u30ed\u30fc\u30d0\u30eb\u30b9\u30b3\u30fc\u30d7\u3067\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/strong>\u30d6\u30e9\u30a6\u30b6\u306e\u30b3\u30f3\u30bd\u30fc\u30eb\u3067<code>this<\/code>\u3092\u4f7f\u3046\u3068\u3001\u7d50\u679c\u306f\u6b21\u306e\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<pre><code>Window {window: Window, self: Window, document: document, name: '', location: Location, ...}<\/code><\/pre>\n<p><code>Window<\/code>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u3059\u3079\u3066\u306e\u30e1\u30bd\u30c3\u30c9\u3068\u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u305d\u3053\u3067\u3001\u30d6\u30e9\u30a6\u30b6\u306e\u30b3\u30f3\u30bd\u30fc\u30eb\u3067<code>this.location<\/code> \u3092\u5b9f\u884c\u3059\u308b\u3068\u3001\u6b21\u306e\u3088\u3046\u306a\u7d50\u679c\u304c\u5f97\u3089\u308c\u307e\u3059\u3002<\/p>\n<pre><code>Location {ancestorOrigins: DOMStringList, href: 'https:\/\/kinsta.com\/', origin: 'https:\/\/kinsta.com', protocol: 'https:', host: 'kinsta.com', ...}<\/code><\/pre>\n<p>\u305d\u3057\u3066\u3001<strong>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u4e2d\u3067<code>this<\/code>\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u305d\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u81ea\u4f53\u3092\u53c2\u7167\u3059\u308b<\/strong>\u3053\u3068\u306b\u306a\u308a\u307e\u3059<strong>\u3002<\/strong>\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u5024\u3092\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u81ea\u4f53\u306e\u30e1\u30bd\u30c3\u30c9\u3067\u53c2\u7167\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const post = { \n\tid: 5,\n\tgetSlug: function(){\n\t\treturn `post-${this.id}`;\n\t},\n\ttitle: 'Awesome post', \n\tcategory: 'JavaScript' \n};\nconsole.log( post.getSlug );<\/code><\/pre>\n<p>\u3067\u306f\u3001<code>this<\/code>\u3092\u95a2\u6570\u306e\u4e2d\u3067\u4f7f\u3063\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-javascript\">const useThis = function () {\n\treturn this;\n}\nconsole.log( useThis() );<\/code><\/pre>\n<p>\u53b3\u5bc6\u30e2\u30fc\u30c9\u3067\u306a\u3044\u5834\u5408\u306f\u3001\u6b21\u306e\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<pre><code>Window {window: Window, self: Window, document: document, name: '', location: Location, ...}<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Strict_mode\" target=\"_blank\" rel=\"noopener noreferrer\">\u53b3\u5bc6\u30e2\u30fc\u30c9<\/a>\u3092\u4f7f\u3046\u3068\u3001\u9055\u3046\u7d50\u679c\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const doSomething = function () {\n\t'use strict';\n\treturn this;\n}\nconsole.log( doSomething() );<\/code><\/pre>\n<p>\u3053\u3053\u3067\u306f\u3001\u95a2\u6570\u306f<code>undefined<\/code>\u3092\u8fd4\u3057\u307e\u3059\u3002\u3053\u308c\u306f\u3001\u95a2\u6570\u5185\u306e<code>this<\/code>\u304c\u3001\u305d\u306e\u660e\u793a\u7684\u306a\u5024\u3092\u53c2\u7167\u3057\u3066\u3044\u308b\u304b\u3089\u3067\u3059\u3002<\/p>\n<p>\u3067\u306f\u3001\u95a2\u6570\u306e\u4e2d\u3067<code>this<\/code>\u3092\u660e\u793a\u7684\u306b\u8a2d\u5b9a\u3059\u308b\u306b\u306f\u3069\u3046\u3059\u308c\u3070\u3088\u3044\u306e\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n<p>\u307e\u305a\u3001\u624b\u52d5\u3067\u30d7\u30ed\u30d1\u30c6\u30a3\u3084\u30e1\u30bd\u30c3\u30c9\u3092\u95a2\u6570\u306b\u5272\u308a\u5f53\u3066\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">function doSomething( post ) {\n\tthis.id = post.id;\n\tthis.title = post.title;\n\tconsole.log( `${this.id} - ${this.title}` );\n}\nnew doSomething( { id: 5, title: 'Awesome post' } );<\/code><\/pre>\n<p><code>call<\/code>\u3001<code>apply<\/code>\u3001<code>bind<\/code>\u30e1\u30bd\u30c3\u30c9\u3084\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u3082\u4f7f\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u95a2\u6570\u306e<code>call()<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3001<code>this<\/code>\u304c\u53c2\u7167\u3059\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u53d7\u3051\u53d6\u308a<\/strong>\u307e\u3059\u3002<\/p>\n<\/aside>\n\n<pre><code class=\"language-javascript\">const doSomething = function() {\n\tconsole.log( `${this.id} - ${this.title}` );\n}\ndoSomething.call( { id: 5, title: 'Awesome post' } );<\/code><\/pre>\n<p><code>call()<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3069\u306e\u3088\u3046\u306a\u95a2\u6570\u3067\u3082\u4f7f\u7528\u3067\u304d\u3001\u305d\u306e\u8a00\u8449\u901a\u308a\u3001\u95a2\u6570\u3092\u547c\u3073\u51fa\u3057\u307e\u3059\u3002<\/p>\n<p>\u3055\u3089\u306b\u3001<code>call()<\/code>\u306f\u3001\u95a2\u6570\u3067\u5b9a\u7fa9\u3055\u308c\u305f\u305d\u306e\u4ed6\u306e\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u53d7\u3051\u4ed8\u3051\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const doSomething = function( cat ) {\n\tconsole.log( `${this.id} - ${this.title} - Category: ${cat}` );\n}\ndoSomething.call( { id: 5, title: 'Awesome post' }, 'JavaScript' );<\/code><\/pre>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<code>apply()<\/code>\u30e1\u30bd\u30c3\u30c9\u306b\u306f\u3001<code>this<\/code>\u304c\u53c2\u7167\u3059\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3068\u3001\u95a2\u6570\u306e\u30d1\u30e9\u30e1\u30fc\u30bf\u306e\u914d\u5217\u304c\u6e21\u3055\u308c\u307e\u3059<\/strong>\u3002<\/p>\n<\/aside>\n\n<pre><code class=\"language-javascript\">const doSomething = function( cat1, cat2 ) {\n\tconsole.log( `${this.id} - ${this.title} - Categories: ${cat1}, ${cat2}` );\n}\ndoSomething.apply( { id: 5, title: 'Awesome post' }, ['JavaScript', 'React'] );<\/code><\/pre>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<code>bind()<\/code>\u30e1\u30bd\u30c3\u30c9\u306f\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3068\u95a2\u6570\u3092\u95a2\u9023\u4ed8\u3051\u3001\u95a2\u6570\u3092\u547c\u3073\u51fa\u3059\u305f\u3073\u306b\u3001<code>this<\/code>\u304c\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u53c2\u7167\u3059\u308b\u3088\u3046\u306b\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<pre><code class=\"language-javascript\">const post = { id: 5, title: 'Awesome post', category: 'JavaScript' };\nconst doSomething = function() {\n\treturn `${this.id} - ${this.title} - ${this.category}`;\n}\nconst bindRender = doSomething.bind( post );\nconsole.log( bindRender() );<\/code><\/pre>\n<p>\u4e0a\u8ff0\u3057\u305f\u65b9\u6cd5\u306e\u4ee3\u308f\u308a\u306b\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Functions\/Arrow_functions\" target=\"_blank\" rel=\"noopener noreferrer\">\u30a2\u30ed\u30fc\u95a2\u6570<\/a>\u3082\u4f7f\u7528\u3067\u304d\u307e\u3059\u3002<\/p>\n<blockquote><p>\u72ec\u81ea\u306e<code>this<\/code><span style=\"font-family: Roboto, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;font-size: 1rem\">\u3092\u6301\u305f\u306a\u3044\u305f\u3081\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u5f0f\u306f\u975e\u30e1\u30bd\u30c3\u30c9\u95a2\u6570\u306b\u306e\u307f\u4f7f\u7528\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/span><\/p><\/blockquote>\n<p>\u3053\u306e\u305f\u3081\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u306f\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u3067\u7279\u306b\u6709\u7528\u3067\u3059\u3002<\/p>\n<p>\u3053\u308c\u306f\u3001\u300c\u30a4\u30f3\u30e9\u30a4\u30f3\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u5c5e\u6027\u304b\u3089\u30b3\u30fc\u30c9\u304c\u547c\u3073\u51fa\u3055\u308c\u308b\u3068\u3001\u305d\u306e<code>this<\/code>\u306f\u30ea\u30b9\u30ca\u30fc\u304c\u914d\u7f6e\u3055\u308c\u3066\u3044\u308bDOM\u8981\u7d20\u306b\u8a2d\u5b9a\u3055\u308c\u308b\u300d\uff08<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/this#this_in_inline_event_handlers\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u53c2\u7167\uff09\u305f\u3081\u3067\u3059\u3002<\/p>\n<p>\u3057\u304b\u3057\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u3067\u306f\u3001\u6b21\u306e\u7406\u7531\u304b\u3089\u72b6\u6cc1\u304c\u5909\u308f\u308a\u307e\u3059\u3002<\/p>\n<blockquote><p>&#8230; \u30a2\u30ed\u30fc\u95a2\u6570\u306f\u3001\u30a2\u30ed\u30fc\u95a2\u6570\u304c\u5b9a\u7fa9\u3055\u308c\u3066\u3044\u308b\u30b9\u30b3\u30fc\u30d7\u306b\u57fa\u3065\u3044\u3066<code>this<\/code>\u3092\u8a2d\u5b9a\u3057\u3001<code>this<\/code>\u306e\u5024\u306f\u3001\u95a2\u6570\u306e\u547c\u3073\u51fa\u3057\u65b9\u306b\u3088\u3063\u3066\u5909\u308f\u308a\u307e\u3059\u3002<\/p><\/blockquote>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u30a2\u30ed\u30fc\u95a2\u6570\u3092\u4f7f\u7528\u3059\u308b\u3068\u3001\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u306b\u76f4\u63a5\u30d0\u30a4\u30f3\u30c9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<h3>React\u3067\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u306b&#8217;this&#8217;\u3092\u30d0\u30a4\u30f3\u30c9\u3059\u308b<\/h3>\n<p>React\u306b\u306f\u3001\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u304c\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5931\u308f\u306a\u3044\u3088\u3046\u306b\u3059\u308b\u65b9\u6cd5\u304c\u3044\u304f\u3064\u304b\u3042\u308a\u307e\u3059\u3002<\/p>\n<p><strong>1. render\u30e1\u30bd\u30c3\u30c9\u5185\u3067<code>bind()<\/code>\u3092\u4f7f\u7528\u3059\u308b<\/strong><\/p>\n<pre><code class=\"language-javascript\">import React, { Component } from 'react';\nclass MyComponent extends Component {\n\tstate = { message: 'Hello World!' };\n\n\tshowMessage(){\n\t\tconsole.log( 'This refers to: ', this );\n\t\tconsole.log( 'The message is: ', this.state.message );\n\t}\n\n\trender(){\n\t\treturn( &lt;button onClick={ this.showMessage.bind( this ) }&gt;Show message from state!&lt;\/button&gt; );\n\t}\n}\nexport default MyComponent;<\/code><\/pre>\n<p><strong>2. \u30b3\u30f3\u30b9\u30c8\u30e9\u30af\u30bf\u3067\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u306b\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u30d0\u30a4\u30f3\u30c9\u3059\u308b<\/strong><\/p>\n<pre><code class=\"language-javascript\">import React, { Component } from 'react';\nclass MyComponent extends Component {\n\tstate = { message: 'Hello World!' };\n\n\tconstructor(props) {\n\t\tsuper(props);\n\t\tthis.showMessage = this.showMessage.bind( this );\n\t}\n\n\tshowMessage(){\n\t\tconsole.log( 'This refers to: ', this );\n\t\tconsole.log( 'The message is: ', this.state.message );\n\t}\n\n\trender(){\n\t\treturn( &lt;button onClick={ this.showMessage }&gt;Show message from state!&lt;\/button&gt; );\n\t}\n}\nexport default MyComponent;<\/code><\/pre>\n<p><strong>3. \u30a2\u30ed\u30fc\u95a2\u6570\u3092\u7528\u3044\u3066\u30a4\u30d9\u30f3\u30c8\u30cf\u30f3\u30c9\u30e9\u3092\u5b9a\u7fa9\u3059\u308b<\/strong><\/p>\n<pre><code class=\"language-javascript\">import React, { Component } from 'react';\nclass MyComponent extends Component {\n\tstate = { message: 'Hello World!' };\n\n\tshowMessage = () =&gt; {\n\t\tconsole.log( 'This refers to: ', this );\n\t\tconsole.log( 'The message is: ', this.state.message );\n\t}\n\n\trender(){\n\t\treturn( &lt;button onClick={this.showMessage}&gt;Show message from state!&lt;\/button&gt; );\n\t}\n}\nexport default MyComponent;<\/code><\/pre>\n<p><strong>4. \u30ec\u30f3\u30c0\u30fc\u30e1\u30bd\u30c3\u30c9\u3067\u30a2\u30ed\u30fc\u95a2\u6570\u3092\u4f7f\u7528\u3059\u308b<\/strong><\/p>\n<pre><code class=\"language-javascript\">import React, { Component } from 'react';\nclass MyComponent extends Component {\n\tstate = { message: 'Hello World!' };\n\n\tshowMessage() {\n\t\tconsole.log( 'This refers to: ', this );\n\t\tconsole.log( 'The message is: ', this.state.message );\n\t}\n\n\trender(){\n\t\treturn( &lt;button onClick={()=&gt;{this.showMessage()}}&gt;Show message from state!&lt;\/button&gt; );\n\t}\n}\nexport default MyComponent;<\/code><\/pre>\n<p>\u3069\u306e\u65b9\u6cd5\u3092\u9078\u629e\u3057\u3066\u3082\u3001\u30dc\u30bf\u30f3\u3092\u30af\u30ea\u30c3\u30af\u3059\u308b\u3068\u3001\u30d6\u30e9\u30a6\u30b6\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u6b21\u306e\u3088\u3046\u306a\u51fa\u529b\u304c\u8868\u793a\u3055\u308c\u307e\u3059\u3002<\/p>\n<pre><code>This refers to:  MyComponent {props: {\u2026}, context: {\u2026}, refs: {\u2026}, updater: {\u2026}, state: {\u2026}, \u2026}\nThe message is:  Hello World!<\/code><\/pre>\n<h2>\u4e09\u9805\u6f14\u7b97\u5b50<\/h2>\n<p><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/Conditional_Operator\" target=\"_blank\" rel=\"noopener noreferrer\">\u6761\u4ef6\u6f14\u7b97\u5b50<\/a>\uff08\u307e\u305f\u306f\u4e09\u9805\u6f14\u7b97\u5b50\uff09\u3092\u4f7f\u3063\u3066\u3001JavaScript\u3067\u7c21\u5358\u306a\u6761\u4ef6\u5f0f\u3092\u8a18\u8ff0\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u30023\u3064\u306e\u88ab\u6f14\u7b97\u5b50\u3092\u3068\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\u6761\u4ef6\u2500\u305d\u306e\u5f8c\u306b\u306f\u3066\u306a\u30de\u30fc\u30af\uff08<code>?<\/code>\uff09\u304c\u7d9a\u304f<\/li>\n<li>\u6761\u4ef6\u304c<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Truthy\" target=\"_blank\" rel=\"noopener noreferrer\">\u771f<\/a>\u3067\u3042\u3063\u305f\u5834\u5408\u306b\u5b9f\u884c\u3059\u308b\u5f0f\u2500\u305d\u306e\u5f8c\u306b\u30bb\u30df\u30b3\u30ed\u30f3\uff08<code>:<\/code>\uff09\u304c\u7d9a\u304f<\/li>\n<li>\u6761\u4ef6\u304c<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Falsy\" target=\"_blank\" rel=\"noopener noreferrer\">\u507d<\/a>\u306e\u5834\u5408\u306b\u5b9f\u884c\u3055\u308c\u308b2\u756a\u76ee\u306e\u5f0f<\/li>\n<\/ul>\n<pre><code class=\"language-javascript\">const drink = personAge &gt;= 18 ? \"Wine\" : \"Juice\";<\/code><\/pre>\n<p>\u307e\u305f\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u8907\u6570\u306e\u5f0f\u3092\u9023\u7d50\u3059\u308b\u3053\u3068\u3082\u53ef\u80fd\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const drink = personAge &gt;= 18 ? \"Wine\" : personAge &gt;= 6 ? \"Juice\" : \"Milk\";<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001\u8907\u6570\u306e\u5f0f\u3092\u9023\u9396\u3055\u305b\u308b\u3053\u3068\u306f\u3001\u4fdd\u5b88\u304c\u56f0\u96e3\u306a\u4e71\u96d1\u306a\u30b3\u30fc\u30c9\u306b\u3064\u306a\u304c\u308b\u53ef\u80fd\u6027\u304c\u3042\u308b\u306e\u3067\u6ce8\u610f\u304c\u5fc5\u8981\u3067\u3059\u3002<\/p>\n<p>\u4e09\u9805\u6f14\u7b97\u5b50\u306f\u3001React\u3001\u7279\u306b\u4e2d\u62ec\u5f27\u5185\u306e\u5f0f\u3057\u304b\u53d7\u3051\u4ed8\u3051\u306a\u3044JSX\u306e\u30b3\u30fc\u30c9\u3067\u7279\u306b\u6709\u7528\u3067\u3059\u3002<\/p>\n<p>\u305f\u3068\u3048\u3070\u3001\u4e09\u9805\u6f14\u7b97\u5b50\u3092\u4f7f\u3046\u3068\u3001\u7279\u5b9a\u306e\u6761\u4ef6\u306b\u57fa\u3065\u3044\u3066\u5c5e\u6027\u306e\u5024\u3092\u8a2d\u5b9a\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">render(){\t\t\t\n\tconst person = {\n\t\tname: 'Carlo',\n\t\tavatar: 'https:\/\/en.gravatar.com\/...',\n\t\tdescription: 'Content Writer',\n\t\ttheme: 'light'\n\t}\n\n\treturn (\n\t\t&lt;div\n\t\t\tclassName='card' \n\t\t\tstyle={\n\t\t\t\tperson.theme === 'dark' ? \n\t\t\t\t{ background: 'black', color: 'white' } : \n\t\t\t\t{ background: 'white', color: 'black'} \n\t\t\t}&gt;\n\t\t\t&lt;img\n\t\t\t\tsrc={person.avatar}\n\t\t\t\talt={person.name}\n\t\t\t\tstyle={ { width: '100%' } }\n\t\t\t\/&gt;\n\t\t\t&lt;div style={ { padding: '2px 16px' } }&gt;\n\t\t\t\t&lt;h3&gt;{person.name}&lt;\/h3&gt;\n\t\t\t\t&lt;p&gt;{person.description}.&lt;\/p&gt;\n\t\t\t&lt;\/div&gt;\n\t\t&lt;\/div&gt;\n\t);\n}<\/code><\/pre>\n<p>\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001\u30b3\u30f3\u30c6\u30ca<code>div<\/code> \u306e<code>style<\/code> \u5c5e\u6027\u306e\u5024\u3092\u8a2d\u5b9a\u3059\u308b\u305f\u3081\u306b\u3001<code>person.theme === 'dark'<\/code>\u3068\u3044\u3046\u6761\u4ef6\u3092\u30c1\u30a7\u30c3\u30af\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<h2>\u77ed\u7d61\u8a55\u4fa1<\/h2>\n<p>AND (<code>&&<\/code>) \u6f14\u7b97\u5b50\u306f\u3001\u88ab\u6f14\u7b97\u5b50\u3092\u5de6\u304b\u3089\u53f3\u306b\u8a55\u4fa1\u3057\u3001\u3059\u3079\u3066\u306e\u88ab\u6f14\u7b97\u5b50\u304c<code>true<\/code>\u3067\u3042\u308b\u5834\u5408\u306b\u306e\u307f\u3001<code>true<\/code>\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<p>AND\u6f14\u7b97\u5b50\u306f<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/Logical_AND#short-circuit_evaluation\" target=\"_blank\" rel=\"noopener noreferrer\">\u77ed\u7d61\u6f14\u7b97\u5b50<\/a>\u3067\u3059\u3002\u5404\u88ab\u6f14\u7b97\u5b50\u306f\u30d6\u30fc\u30eb\u5024\u306b\u5909\u63db\u3055\u308c\u3001\u5909\u63db\u7d50\u679c\u304c<code>false<\/code>\u306e\u5834\u5408\u3001AND\u6f14\u7b97\u5b50\u306f\u505c\u6b62\u3057\u3001falsy\u306a\u88ab\u6f14\u7b97\u5b50\u306e\u5143\u306e\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002\u3059\u3079\u3066\u306e\u5024\u304c<code>true<\/code>\u3067\u3042\u308c\u3070\u3001\u6700\u5f8c\u306e\u88ab\u6f14\u7b97\u5b50\u306e\u5143\u306e\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<p><aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f JavaScript\u3067\u306f\u3001<code>true &amp;&amp; expression<\/code>\u306f\u5e38\u306b<code>expression<\/code>\u3092\u8fd4\u3057\u3001<code>false &amp;&amp; expression<\/code>\u306f\u5e38\u306b<code>false<\/code> \u3092\u8fd4\u3057\u307e\u3059<\/strong>\u3002<\/p>\n<\/aside>\n<strong><br \/>\n<\/strong><br \/>\n\u77ed\u7d61\u8a55\u4fa1\u306f\u3001\u7279\u5b9a\u306e\u6761\u4ef6\u306b\u57fa\u3065\u3044\u3066\u30b3\u30fc\u30c9\u306e\u30d6\u30ed\u30c3\u30af\u3092\u51fa\u529b\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u305f\u3081\u3001React\u3067\u3088\u304f\u4f7f\u7528\u3055\u308c\u308bJavaScript\u306e\u6a5f\u80fd\u3067\u3059\u3002<a href=\"https:\/\/kinsta.com\/blog\/dynamic-blocks\/#add-the-excerpt\">\u4ee5\u4e0b\u306e\u4f8b<\/a>\u3092\u3054\u89a7\u304f\u3060\u3055\u3044\u3002<\/p>\n<pre><code class=\"language-jsx\">{\n\tdisplayExcerpt &&\n\tpost.excerpt.rendered && (\n\t\t&lt;p&gt;\n\t\t\t&lt;RawHTML&gt;\n\t\t\t\t{ post.excerpt.rendered }\n\t\t\t&lt;\/RawHTML&gt;\n\t\t&lt;\/p&gt;\n\t)\n}<\/code><\/pre>\n<p>\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u3001<code>displayExcerpt<\/code><strong>\u3068<\/strong><code>post.excerpt.rendered<\/code>\u304c<code>true<\/code>\u3068\u3057\u3066\u8a55\u4fa1\u3055\u308c\u308b\u3068\u3001React\u306fJSX\u306e\u6700\u7d42\u30d6\u30ed\u30c3\u30af\u3092\u8fd4\u3057\u307e\u3059\u3002<\/p>\n<p><a href=\"https:\/\/legacy.reactjs.org\/docs\/conditional-rendering.html#inline-if-with-logical--operator\" target=\"_blank\" rel=\"noopener noreferrer\">\u8981\u7d04<\/a>\u3059\u308b\u3068\u300c\u6761\u4ef6\u304c<code>true<\/code>\u306e\u5834\u5408\u3001<code>&&<\/code>\u306e\u76f4\u5f8c\u306e\u8981\u7d20\u304c\u51fa\u529b\u306b\u8868\u793a\u3055\u308c\u307e\u3059\u3002<code>false<\/code>\u306e\u5834\u5408\u306f\u3001React\u306f\u305d\u308c\u3092\u7121\u8996\u3057\u30b9\u30ad\u30c3\u30d7\u300d\u3057\u307e\u3059\u3002<\/p>\n<h2>\u30b9\u30d7\u30ec\u30c3\u30c9\u69cb\u6587<\/h2>\n<p>JavaScript\u3067\u306f\u3001\u914d\u5217\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306a\u3069\u306e\u53cd\u5fa9\u53ef\u80fd\u306a\u8981\u7d20\u3092\u3001\u95a2\u6570\u5f15\u6570\u3001\u914d\u5217\u30ea\u30c6\u30e9\u30eb\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u30ea\u30c6\u30e9\u30eb\u306b\u5c55\u958b\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/Spread_syntax\" target=\"_blank\" rel=\"noopener noreferrer\">\u30b9\u30d7\u30ec\u30c3\u30c9\u69cb\u6587<\/a>\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u6b21\u306e\u4f8b\u3067\u306f\u3001\u95a2\u6570\u547c\u3073\u51fa\u3057\u306e\u4e2d\u3067\u914d\u5217\u3092\u5c55\u958b\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">function doSomething( x, y, z ){\n\treturn `First: ${x} - Second: ${y} - Third: ${z} - Sum: ${x+y+z}`;\n}\nconst numbers = [3, 4, 7];\nconsole.log( doSomething( ...numbers ) );<\/code><\/pre>\n<p>\u914d\u5217\u306e\u8907\u88fd\uff08\u591a\u6b21\u5143\u914d\u5217\u3082\u53ef\uff09\u3084\u914d\u5217\u306e\u9023\u7d50\u306b\u306f\u3001\u30b9\u30d7\u30ec\u30c3\u30c9\u69cb\u6587\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u4ee5\u4e0b\u306e\u4f8b\u3067\u306f\u30012\u3064\u306e\u914d\u5217\u30922\u3064\u306e\u7570\u306a\u308b\u65b9\u6cd5\u3067\u9023\u7d50\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">const firstArray = [1, 2, 3];\nconst secondArray = [4, 5, 6];\nfirstArray.push( ...secondArray );\nconsole.log( firstArray );<\/code><\/pre>\n<p>\u5225\u306e\u65b9\u6cd5\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">let firstArray = [1, 2, 3];\nconst secondArray = [4, 5, 6];\nfirstArray = [ ...firstArray, ...secondArray];\nconsole.log( firstArray );<\/code><\/pre>\n<p>\u30b9\u30d7\u30ec\u30c3\u30c9\u69cb\u6587\u3092\u4f7f\u7528\u3057\u3066\u30012\u3064\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u8907\u88fd\u307e\u305f\u306f\u7d50\u5408\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-jsx\">const firstObj = { id: '1', title: 'JS is awesome' };\nconst secondObj = { cat: 'React', description: 'React is easy' };\n\n\/\/ clone object\nconst thirdObj = { ...firstObj };\n\n\/\/ merge objects\nconst fourthObj = { ...firstObj, ...secondObj }\n\nconsole.log( { ...thirdObj } );\nconsole.log( { ...fourthObj } );<\/code><\/pre>\n<h2>\u5206\u5272\u4ee3\u5165<\/h2>\n<p>React\u3067\u3088\u304f\u4f7f\u308f\u308c\u308b\u3082\u3046\u4e00\u3064\u306e\u69cb\u6587\u304c\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/Destructuring_assignment\" target=\"_blank\" rel=\"noopener noreferrer\">\u5206\u5272\u4ee3\u5165<\/a>\u3067\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u5206\u5272\u4ee3\u5165\u3067\u306f\u3001\u914d\u5217\u306e\u5024\u3084\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u5225\u306e\u5909\u6570\u306b\u5c55\u958b\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u6b21\u306e\u4f8b\u3067\u306f\u3001\u914d\u5217\u304b\u3089\u5024\u3092\u5206\u89e3\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const user = ['Carlo', 'Content writer', 'Kinsta'];\nconst [name, description, company] = user;\nconsole.log( `${name} is ${description} at ${company}` );<\/code><\/pre>\n<p>\u307e\u305f\u3001\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4f7f\u3063\u305f\u5206\u5272\u4ee3\u5165\u306e\u7c21\u5358\u306a\u4f8b\u3092\u793a\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const user = {\n\tname: 'Carlo',\n\tdescription: 'Content writer',\n\tcompany: 'Kinsta'\n}\nconst { name, description, company } = user;\nconsole.log( `${name} is ${description} at ${company}` );<\/code><\/pre>\n<p>\u3053\u308c\u306b\u3068\u3069\u307e\u3089\u305a\u3001\u591a\u304f\u306e\u3053\u3068\u3092\u884c\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u4f8b\u3067\u306f\u3001\u3042\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u3044\u304f\u3064\u304b\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u53d6\u308a\u51fa\u3057\u3001\u6b8b\u308a\u306e\u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u30b9\u30d7\u30ec\u30c3\u30c9\u69cb\u6587\u3092\u4f7f\u7528\u3057\u5225\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u5272\u308a\u5f53\u3066\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const user = {\n\tname: 'Carlo',\n\tfamily: 'Daniele',\n\tdescription: 'Content writer',\n\tcompany: 'Kinsta',\n\tpower: 'swimming'\n}\nconst { name, description, company, ...rest } = user;\nconsole.log( rest ); \/\/ {family: 'Daniele', power: 'swimming'}<\/code><\/pre>\n<p>\u307e\u305f\u3001\u914d\u5217\u306b\u5024\u3092\u4ee3\u5165\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const user = [];\nconst object = { name: 'Carlo', company: 'Kinsta' };\n( { name: user[0], company: user[1] } = object );\nconsole.log( user ); \/\/ (2) ['Carlo', 'Kinsta']<\/code><\/pre>\n<p>\u306a\u304a\u3001\u5ba3\u8a00\u3092\u4f34\u308f\u306a\u3044\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u30ea\u30c6\u30e9\u30eb\u306b\u3088\u308b\u5206\u5272\u4ee3\u5165\u306e\u5834\u5408\u306f\u3001\u4ee3\u5165\u6587\u306e\u5468\u308a\u306b\u62ec\u5f27\u304c\u5fc5\u8981\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<p>\u5206\u5272\u4ee3\u5165\u306e\u8a73\u7d30\u306a\u8aac\u660e\u3068\u4f7f\u7528\u4f8b\u306b\u3064\u3044\u3066\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Operators\/Destructuring_assignment\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u3092\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<h2>filter(), map(), reduce()<\/h2>\n<p>JavaScript\u306b\u306f\u3001React\u3067\u3088\u304f\u4f7f\u308f\u308c\u308b\u4fbf\u5229\u306a\u30e1\u30bd\u30c3\u30c9\u304c\u3044\u304f\u3064\u304b\u3042\u308a\u307e\u3059\u3002<\/p>\n<h3>filter()<\/h3>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Array\/filter\" target=\"_blank\" rel=\"noopener noreferrer\"><code>filter()<\/code>\u30e1\u30bd\u30c3\u30c9<\/a>\u306f\u3001\u4e0e\u3048\u3089\u308c\u305f\u914d\u5217\u306e\u4e00\u90e8\u304b\u3089\u3001\u6307\u5b9a\u3055\u308c\u305f\u95a2\u6570\u306e\u6761\u4ef6\u3092\u6e80\u305f\u3059\u8981\u7d20\u3092\u7d5e\u308a\u8fbc\u307f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Glossary\/Shallow_copy\" target=\"_blank\" rel=\"noopener noreferrer\">\u6d45\u3044\u30b3\u30d4\u30fc<\/a>\u3092\u4f5c\u6210<\/strong>\u3057\u307e\u3059\u3002<\/p>\n<\/aside>\n\n<p>\u6b21\u306e\u4f8b\u3067\u306f\u3001<code>numbers<\/code>\u306e\u914d\u5217\u306b\u30d5\u30a3\u30eb\u30bf\u3092\u9069\u7528\u3057\u3066\u3001\u8981\u7d20\u304c5\u3088\u308a\u5927\u304d\u3044\u6570\u5024\u3067\u3042\u308b\u914d\u5217\u3092\u53d6\u5f97\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const numbers = [2, 6, 8, 2, 5, 9, 23];\nconst result = numbers.filter( number =&gt; number &gt; 5);\nconsole.log(result); \/\/ (4) [6, 8, 9, 23]<\/code><\/pre>\n<p>\u6b21\u306e\u4f8b\u3067\u306f\u3001\u30bf\u30a4\u30c8\u30eb\u306b\u300cJavaScript\u300d\u3068\u3044\u3046\u5358\u8a9e\u304c\u542b\u307e\u308c\u308b\u6295\u7a3f\u306e\u914d\u5217\u3092\u53d6\u5f97\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const posts = [\n\t{id: 0, title: 'JavaScript is awesome', content: 'your content'},\n\t{id: 1, title: 'WordPress is easy', content: 'your content'},\n\t{id: 2, title: 'React is cool', content: 'your content'},\n\t{id: 3, title: 'With JavaScript to the moon', content: 'your content'},\n];\n\nconst jsPosts = posts.filter( post =&gt; post.title.includes( 'JavaScript' ) );\n\nconsole.log( jsPosts );<\/code><\/pre>\n<figure id=\"attachment_152106\" aria-describedby=\"caption-attachment-152106\" style=\"width: 1198px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-152106 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/filter.jpg\" alt=\"\u30bf\u30a4\u30c8\u30eb\u306b'JavaScript'\u304c\u542b\u307e\u308c\u308b\u6295\u7a3f\u306e\u914d\u5217\" width=\"1198\" height=\"346\"><figcaption id=\"caption-attachment-152106\" class=\"wp-caption-text\">\u30bf\u30a4\u30c8\u30eb\u306b&#8217;JavaScript&#8217;\u304c\u542b\u307e\u308c\u308b\u6295\u7a3f\u306e\u914d\u5217<\/figcaption><\/figure>\n<h3>map()<\/h3>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Array\/map\" target=\"_blank\" rel=\"noopener noreferrer\"><code>map()<\/code>\u30e1\u30bd\u30c3\u30c9<\/a>\u306f\u3001\u914d\u5217\u306e\u5404\u8981\u7d20\u306b\u5bfe\u3057\u3066\u6307\u5b9a\u3055\u308c\u305f\u95a2\u6570\u3092\u5b9f\u884c\u3057\u3001\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u306e\u7d50\u679c\u3068\u3057\u3066\u5f97\u3089\u308c\u305f\u5404\u8981\u7d20\u3092\u542b\u3080\u65b0\u3057\u3044\u914d\u5217\u3092\u8fd4\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<pre><code class=\"language-javascript\">const numbers = [2, 6, 8, 2, 5, 9, 23];\nconst result = numbers.map( number =&gt; number * 5 );\nconsole.log(result); \/\/ (7) [10, 30, 40, 10, 25, 45, 115]<\/code><\/pre>\n<p>React\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u306f\u3001<code>map()<\/code>\u30e1\u30bd\u30c3\u30c9\u304c\u30ea\u30b9\u30c8\u3092\u69cb\u7bc9\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3055\u308c\u308b\u3053\u3068\u304c\u3088\u304f\u3042\u308a\u307e\u3059\u3002\u6b21\u306e\u4f8b\u3067\u306f\u3001WordPress\u306e<code>posts<\/code>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u5bfe\u8c61\u306b\u3057\u3066\u3001<a href=\"https:\/\/kinsta.com\/blog\/dynamic-blocks\/\">\u6295\u7a3f\u306e\u30ea\u30b9\u30c8\u3092\u69cb\u7bc9<\/a>\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">&lt;ul&gt;\n\t{ posts && posts.map( ( post ) =&gt; {\n\t\treturn (\n\t\t\t&lt;li key={ post.id }&gt;\n\t\t\t\t&lt;h5&gt;\n\t\t\t\t\t&lt;a href={ post.link }&gt;\n\t\t\t\t\t\t{ \n\t\t\t\t\t\t\tpost.title.rendered ? \n\t\t\t\t\t\t\tpost.title.rendered :\n\t\t\t\t\t\t\t__( 'Default title', 'author-plugin' )\n\t\t\t\t\t\t}\n\t\t\t\t\t&lt;\/a&gt;\n\t\t\t\t&lt;\/h5&gt;\n\t\t\t&lt;\/li&gt;\n\t\t)\n\t})}\n&lt;\/ul&gt;<\/code><\/pre>\n<h3>reduce()<\/h3>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Array\/reduce\" target=\"_blank\" rel=\"noopener noreferrer\"><code>reduce()<\/code>\u30e1\u30bd\u30c3\u30c9<\/a>\u306f\u3001\u914d\u5217\u306e\u5404\u8981\u7d20\u306b\u5bfe\u3057\u3066\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\uff08reducer\uff09\u3092\u5b9f\u884c\u3057\u3001\u305d\u306e\u623b\u308a\u5024\u3092\u6b21\u306e\u53cd\u5fa9\u51e6\u7406\u306b\u6e21\u3057\u307e\u3059\u3002\u8981\u3059\u308b\u306b\u3001reducer\u306f\u914d\u5217\u306e\u3059\u3079\u3066\u306e\u8981\u7d20\u30921\u3064\u306e\u5024\u306b\u300c\u9084\u5143\u300d\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p><code>reduce()<\/code>\u306f\u30012\u3064\u306e\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u53d7\u3051\u53d6\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\u914d\u5217\u306e\u5404\u8981\u7d20\u306b\u5bfe\u3057\u3066\u5b9f\u884c\u3055\u308c\u308b\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\uff1a\u3053\u306e\u95a2\u6570\u306f\u3001\u6b21\u306e\u547c\u3073\u51fa\u3057\u3067\u84c4\u7a4d\u30d1\u30e9\u30e1\u30fc\u30bf\u306e\u5024\u3068\u306a\u308b\u5024\u3092\u8fd4\u3057\u307e\u3059\u3002\u6700\u5f8c\u306e\u547c\u3073\u51fa\u3057\u3067\u3001\u3053\u306e\u95a2\u6570\u304b\u3089\u306f<code>reduce()<\/code>\u306e\u623b\u308a\u5024\u3068\u306a\u308b\u5024\u304c\u8fd4\u3055\u308c\u307e\u3059\u3002<\/li>\n<li>\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u306b\u6e21\u3055\u308c\u308b\u84c4\u7a4d\u306e\u6700\u521d\u306e\u5024\u3067\u3042\u308b\u521d\u671f\u5024<\/li>\n<\/ul>\n<p>\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u306f\u3044\u304f\u3064\u304b\u306e\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u3068\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li><strong>\u30a2\u30ad\u30e5\u30e0\u30ec\u30fc\u30bf<\/strong>\uff1a\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u3092\u524d\u56de\u547c\u3073\u51fa\u3057\u305f\u3068\u304d\u306b\u8fd4\u3055\u308c\u305f\u5024\u3067\u3059\u3002\u6700\u521d\u306e\u547c\u3073\u51fa\u3057\u3067\u306f\u3001\u6307\u5b9a\u3055\u308c\u305f\u5834\u5408\u3001\u521d\u671f\u5024\u306b\u8a2d\u5b9a\u3055\u308c\u307e\u3059\u3002\u305d\u3046\u3067\u306a\u3044\u5834\u5408\u306f\u3001\u914d\u5217\u306e\u6700\u521d\u306e\u9805\u76ee\u306e\u5024\u3092\u3068\u308a\u307e\u3059\u3002<\/li>\n<li><strong>\u73fe\u5728\u306e\u8981\u7d20<\/strong>\u306e\u5024\uff1a\u521d\u671f\u5024\u304c\u8a2d\u5b9a\u3055\u308c\u3066\u3044\u308b\u5834\u5408\u306f\u914d\u5217\u306e1\u756a\u76ee\u306e\u8981\u7d20\uff08<code>array[0]<\/code>\uff09\u3001\u305d\u308c\u4ee5\u5916\u306e\u5834\u5408\u306f2\u756a\u76ee\u306e\u8981\u7d20\uff08<code>array[1]<\/code>\uff09\u306e\u5024\u304c\u8a2d\u5b9a\u3055\u308c\u307e\u3059\u3002<\/li>\n<li><strong>\u73fe\u5728\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9<\/strong>\uff1a\u73fe\u5728\u306e\u8981\u7d20\u306e\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u4f4d\u7f6e\u3092\u6307\u3057\u307e\u3059\u3002<\/li>\n<\/ul>\n<p>\u3053\u308c\u3092\u7406\u89e3\u3059\u308b\u305f\u3081\u306b\u3001\u4f8b\u3092\u6319\u3052\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const numbers = [1, 2, 3, 4, 5];\nconst initialValue = 0;\nconst sumElements = numbers.reduce(\n\t( accumulator, currentValue ) =&gt; accumulator + currentValue,\n\tinitialValue\n);\nconsole.log( numbers ); \/\/ (5) [1, 2, 3, 4, 5]\nconsole.log( sumElements ); \/\/ 15<\/code><\/pre>\n<p>\u5404\u53cd\u5fa9\u3067\u4f55\u304c\u8d77\u3053\u308b\u304b\u3001\u8a73\u3057\u304f\u8abf\u3079\u3066\u307f\u307e\u3057\u3087\u3046\u3002\u524d\u306e\u4f8b\u306b\u623b\u3063\u3066\u3001<code>initialValue<\/code>\u3092\u5909\u66f4\u3057\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">const numbers = [1, 2, 3, 4, 5];\nconst initialValue = 5;\nconst sumElements = numbers.reduce(\n\t( accumulator, currentValue, index ) =&gt; {\n\t\tconsole.log('Accumulator: ' + accumulator + ' - currentValue: ' + currentValue + ' - index: ' + index);\n\t\treturn accumulator + currentValue;\n\t},\n\tinitialValue\n);\nconsole.log( sumElements );<\/code><\/pre>\n<p>\u6b21\u306e\u753b\u50cf\u306f\u3001\u30d6\u30e9\u30a6\u30b6\u306e\u30b3\u30f3\u30bd\u30fc\u30eb\u306b\u51fa\u529b\u3055\u308c\u305f\u7d50\u679c\u3067\u3059\u3002<\/p>\n<figure id=\"attachment_152231\" aria-describedby=\"caption-attachment-152231\" style=\"width: 1172px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-152231 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/reduce-with-initial-value.jpg\" alt=\"\u521d\u671f\u5024\u30925\u306b\u8a2d\u5b9a\u3057reduce()\u3092\u4f7f\u7528\" width=\"1172\" height=\"388\"><figcaption id=\"caption-attachment-152231\" class=\"wp-caption-text\">\u521d\u671f\u5024\u30925\u306b\u8a2d\u5b9a\u3057reduce()\u3092\u4f7f\u7528<\/figcaption><\/figure>\n<p>\u3067\u306f\u3001<code>initialValue<\/code>\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u6307\u5b9a\u3057\u306a\u3044\u5834\u5408\u3001\u3069\u3046\u306a\u308b\u304b\u3092\u898b\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre><code class=\"language-javascript\">const numbers = [1, 2, 3, 4, 5];\nconst sumElements = numbers.reduce(\n\t( accumulator, currentValue, index ) =&gt; {\n\t\tconsole.log( 'Accumulator: ' + accumulator + ' - currentValue: ' + currentValue + ' - index: ' + index );\n\t\treturn accumulator + currentValue;\n\t}\n);\nconsole.log( sumElements );<\/code><\/pre>\n<figure id=\"attachment_152232\" aria-describedby=\"caption-attachment-152232\" style=\"width: 1176px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-152232 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/reduce-without-initial-value.jpg\" alt=\"\u521d\u671f\u5024\u306a\u3057\u3067reduce()\u3092\u4f7f\u7528\u3059\u308b\" width=\"1176\" height=\"360\"><figcaption id=\"caption-attachment-152232\" class=\"wp-caption-text\">\u521d\u671f\u5024\u306a\u3057\u3067reduce()\u3092\u4f7f\u7528\u3059\u308b<\/figcaption><\/figure>\n<p>\u305d\u306e\u4ed6\u306e\u4f7f\u7528\u4f8b\u306b\u3064\u3044\u3066\u306f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Array\/reduce\" target=\"_blank\" rel=\"noopener noreferrer\">mdn web docs<\/a>\u3092\u3054\u89a7\u304f\u3060\u3055\u3044\u3002<\/p>\n<h2>\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3068\u30a4\u30f3\u30dd\u30fc\u30c8<\/h2>\n<p>ECMAScript 2015 (ES6) \u306e\u6642\u70b9\u3067\u3001JavaScript \u30e2\u30b8\u30e5\u30fc\u30eb\u304b\u3089\u5024\u3092\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3057\u3001\u5225\u306e\u30b9\u30af\u30ea\u30d7\u30c8\u306b\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002React\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3067\u306f\u3001\u30a4\u30f3\u30dd\u30fc\u30c8\u3068\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3092\u5e83\u7bc4\u56f2\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u306b\u306a\u308b\u305f\u3081\u3001\u305d\u306e\u4ed5\u7d44\u307f\u3092\u3088\u304f\u7406\u89e3\u3057\u3066\u304a\u304f\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\u3002<\/p>\n<p>\u6b21\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001\u6a5f\u80fd\u7684\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u4f5c\u6210\u3057\u3066\u3044\u307e\u3059\u3002\u6700\u521d\u306e\u884c\u3067\u3001React\u30e9\u30a4\u30d6\u30e9\u30ea\u3092\u30a4\u30f3\u30dd\u30fc\u30c8\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">import React from 'react';\n\nfunction MyComponent() {\n\tconst person = {\n\t\tname: 'Carlo',\n\t\tavatar: 'https:\/\/en.gravatar.com\/userimage\/954861\/fc68a728946aac04f8531c3a8742ac22?size=original',\n\t\tdescription: 'Content Writer',\n\t\ttheme: 'dark'\n\t}\n \n\treturn (\n\t\t&lt;div\n\t\t\tclassName = 'card'\n\t\t\tstyle = {\n\t\t\t\tperson.theme === 'dark' ?\n\t\t\t\t{ background: 'black', color: 'white' } :\n\t\t\t\t{ background: 'white', color: 'black'}\n\t\t\t}&gt;\n\t\t\t&lt;img\n\t\t\t\tsrc = { person.avatar }\n\t\t\t\talt = { person.name }\n\t\t\t\tstyle = { { width: '100%' } }\n\t\t\t\/&gt;\n\t\t\t&lt;div\n\t\t\t\tstyle = { { padding: '2px 16px' } }\n\t\t\t&gt;\n\t\t\t\t&lt;h3&gt;{ person.name }&lt;\/h3&gt;\n\t\t\t\t&lt;p&gt;{ person.description }.&lt;\/p&gt;\n\t\t\t&lt;\/div&gt;\n\t\t&lt;\/div&gt;\n\t);\n}\nexport default MyComponent;<\/code><\/pre>\n<p>\u4e0a\u306e\u4f8b\u3067\u306f\u3001<code>import<\/code>\u306e\u5f8c\u306b\u3001\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u3082\u306e\u306b\u5272\u308a\u5f53\u3066\u305f\u3044\u540d\u524d\u3092\u4ed8\u3051\u3001\u305d\u306e\u5f8c\u306b<strong>package.json<\/strong>\u30d5\u30a1\u30a4\u30eb\u3067\u53c2\u7167\u3055\u308c\u3066\u3044\u308b\u30a4\u30f3\u30b9\u30c8\u30fc\u30eb\u3057\u305f\u3044\u30d1\u30c3\u30b1\u30fc\u30b8\u306e\u540d\u524d\u3092\u4ed8\u3051\u3066\u3044\u307e\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<code>import<\/code>\u306f\u3001\u4ed6\u306e\u30e2\u30b8\u30e5\u30fc\u30eb\u306b\u3088\u3063\u3066\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3055\u308c\u305f\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/import\" target=\"_blank\" rel=\"noopener noreferrer\">\u8aad\u307f\u53d6\u308a\u5c02\u7528\u306e\u30e9\u30a4\u30d6\u30d0\u30a4\u30f3\u30c7\u30a3\u30f3\u30b0\u3092\u30a4\u30f3\u30dd\u30fc\u30c8<\/a>\u3059\u308b\u306e\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u4e0a\u8a18\u306e<code>MyComponent()<\/code>\u95a2\u6570\u3067\u306f\u3001\u524d\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u8aac\u660e\u3057\u305f JavaScript\u306e\u6a5f\u80fd\u306e\u3044\u304f\u3064\u304b\u3092\u4f7f\u7528\u3057\u3066\u3044\u307e\u3059\u3002\u4e2d\u62ec\u5f27\u306e\u4e2d\u306b\u30d7\u30ed\u30d1\u30c6\u30a3\u5024\u3092\u542b\u3081\u3001\u6761\u4ef6\u6f14\u7b97\u5b50\u306e\u69cb\u6587\u3092\u4f7f\u3063\u3066<code>style<\/code>\u30d7\u30ed\u30d1\u30c6\u30a3\u306e\u5024\u3092\u4ee3\u5165\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u6700\u5f8c\u306b\u30ab\u30b9\u30bf\u30e0\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3092\u884c\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u30a4\u30f3\u30dd\u30fc\u30c8\u3068\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u306b\u3064\u3044\u3066\u5927\u67a0\u3092\u7406\u89e3\u3057\u305f\u3068\u3053\u308d\u3067\u3001\u305d\u306e\u4ed5\u7d44\u307f\u306b\u3064\u3044\u3066\u8a73\u3057\u304f\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n<h3 id=\"export\" class=\"has-anchor-hash\">Export<\/h3>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f<code>export<\/code>\u306f\u3001JavaScript\u30e2\u30b8\u30e5\u30fc\u30eb\u304b\u3089\u5024\u3092\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3059\u308b\u306e\u306b\u4f7f\u7528\u3055\u308c\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u3059\u3079\u3066\u306eReact\u30e2\u30b8\u30e5\u30fc\u30eb\u3067\u3001<a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/export#description\" target=\"_blank\" rel=\"noopener noreferrer\">2\u7a2e\u985e\u306e\u30a8\u30af\u30b9\u30dd\u30fc\u30c8<\/a>\u304c\u5229\u7528\u3067\u304d\u307e\u3059\u3002\u305d\u308c\u304c\u3001<strong>\u540d\u524d\u4ed8\u304d\u30a8\u30af\u30b9\u30dd\u30fc\u30c8<\/strong>\u3068<strong>\u30c7\u30d5\u30a9\u30eb\u30c8\u30a8\u30af\u30b9\u30dd\u30fc\u30c8<\/strong>\u3067\u3059\u3002<\/p>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u30e2\u30b8\u30e5\u30fc\u30eb\u3054\u3068\u306b\u8907\u6570\u306e\u540d\u524d\u4ed8\u304d\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3092\u6301\u3064\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u304c\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u306f1\u3064\u3060\u3051\u3067\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p>\u4f8b\u3048\u3070\u30011\u3064\u306e<code>export<\/code>\u6587\u3067\u8907\u6570\u306e\u6a5f\u80fd\u3092\u4e00\u5ea6\u306b\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">export { MyComponent, MyVariable };<\/code><\/pre>\n<p>\u307e\u305f\u3001\u500b\u3005\u306e\u6a5f\u80fd\u3092\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059 \uff08<code>function<\/code>\u3001<code>class<\/code>\u3001<code>const<\/code>\u3001<code>let<\/code>\uff09\u3002<\/p>\n<pre><code class=\"language-javascript\">export function MyComponent() { ... };\nexport let myVariable = x + y;<\/code><\/pre>\n<p>\u3057\u304b\u3057\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u306f1\u3064\u3057\u304b\u3067\u304d\u307e\u305b\u3093\u3002<\/p>\n<pre><code class=\"language-javascript\">export default MyComponent;<\/code><\/pre>\n<p>\u307e\u305f\u3001\u500b\u3005\u306e\u6a5f\u80fd\u306b\u5bfe\u3057\u3066\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3092\u4f7f\u7528\u3059\u308b\u3053\u3068\u3082\u53ef\u80fd\u3067\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">export default function() { ... }\nexport default class { ... }<\/code><\/pre>\n<h3 id=\"import\" class=\"has-anchor-hash\">Import<\/h3>\n<p>\u4e00\u5ea6\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u3055\u308c\u305f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306f\u3001\u4ed6\u306e\u30e2\u30b8\u30e5\u30fc\u30eb\u3068\u4e00\u7dd2\u306b\u5225\u306e\u30d5\u30a1\u30a4\u30eb\u3001\u4f8b\u3048\u3070<strong>index.js<\/strong>\u30d5\u30a1\u30a4\u30eb\u306b\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre><code class=\"language-javascript\">import React from 'react';\nimport ReactDOM from 'react-dom\/client';\nimport '.\/index.css';\nimport MyComponent from '.\/MyComponent';\n\nconst root = ReactDOM.createRoot( document.getElementById( 'root' ) );\nroot.render(\n\t&lt;React.StrictMode&gt;\n\t\t&lt;MyComponent \/&gt;\n\t&lt;\/React.StrictMode&gt;\n);<\/code><\/pre>\n<p>\u4e0a\u306e\u30b3\u30fc\u30c9\u3067\u306f\u3001import\u3092\u3044\u304f\u3064\u304b\u306e\u65b9\u6cd5\u3067\u4f7f\u7528\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u6700\u521d\u306e2\u884c\u3067\u306f\u3001\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u30ea\u30bd\u30fc\u30b9\u306b\u540d\u524d\u3092\u4ed8\u3051\u30013\u884c\u76ee\u3067\u306f\u540d\u524d\u3092\u4ed8\u3051\u305a\u3001\u5358\u306b<strong>.\/index.css<\/strong>\u30d5\u30a1\u30a4\u30eb\u3092\u30a4\u30f3\u30dd\u30fc\u30c8\u3057\u3066\u3044\u307e\u3059\u3002\u6700\u5f8c\u306e<code>import<\/code>\u6587\u3067\u306f\u3001<strong>.\/MyComponent<\/strong>\u30d5\u30a1\u30a4\u30eb\u3092\u30a4\u30f3\u30dd\u30fc\u30c8\u3057\u3066\u540d\u524d\u3092\u5272\u308a\u5f53\u3066\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>\u305d\u308c\u3067\u306f\u3001\u3053\u308c\u3089\u306e\u30a4\u30f3\u30dd\u30fc\u30c8\u306e\u9055\u3044\u3092\u78ba\u8a8d\u3057\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<p>\u30a4\u30f3\u30dd\u30fc\u30c8\u306b\u306f\u5168\u90e8\u30674\u7a2e\u985e\u3042\u308a\u307e\u3059\u3002<\/p>\n<p><strong>\u540d\u524d\u4ed8\u304d\u30a4\u30f3\u30dd\u30fc\u30c8<\/strong><\/p>\n<pre><code class=\"language-javascript\">import { MyFunction, MyVariable } from \".\/my-module\";<\/code><\/pre>\n<p><strong>\u30c7\u30d5\u30a9\u30eb\u30c8\u30a4\u30f3\u30dd\u30fc\u30c8<\/strong><\/p>\n<pre><code class=\"language-javascript\">import MyComponent from \".\/MyComponent\";<\/code><\/pre>\n<p><strong>namespace\u30a4\u30f3\u30dd\u30fc\u30c8<\/strong><\/p>\n<pre><code class=\"language-javascript\">import * as name from \"my-module\";<\/code><\/pre>\n<p><strong>side effect\u30a4\u30f3\u30dd\u30fc\u30c8<\/strong><\/p>\n<pre><code class=\"language-javascript\">import \"module-name\";<\/code><\/pre>\n<aside role=\"note\" class=\"wp-block-kinsta-notice is-style-plain\">\n        <p><strong>\u270d\ufe0f \u4e2d\u62ec\u5f27\u306e\u306a\u3044<code>import<\/code>\u6587\u306f\u3001\u30c7\u30d5\u30a9\u30eb\u30c8\u306e<code>export<\/code>\u3092\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u306e\u306b\u4f7f\u7528\u3057\u307e\u3059\u3002\u4e2d\u62ec\u5f27\u4ed8\u304d\u306e<code>import<\/code>\u6587\u306f\u3001\u540d\u524d\u4ed8\u304d<code>export<\/code>\u3092\u30a4\u30f3\u30dd\u30fc\u30c8\u3059\u308b\u306e\u306b\u4f7f\u7528\u3057\u307e\u3059\u3002<\/strong><\/p>\n<\/aside>\n\n<p><strong>index.css<\/strong>\u306b\u30b9\u30bf\u30a4\u30eb\u3092\u9069\u7528\u3059\u308b\u3068\u3001\u4ee5\u4e0b\u306e\u753b\u50cf\u306e\u3088\u3046\u306b\uff08\u5bfe\u5fdc\u3059\u308bHTML\u30b3\u30fc\u30c9\u3068\u3042\u308f\u305b\u3066\uff09\u30ab\u30fc\u30c9\u304c\u8868\u793a\u3055\u308c\u307e\u3059\u3002<\/p>\n<figure id=\"attachment_152317\" aria-describedby=\"caption-attachment-152317\" style=\"width: 1806px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-152317 size-full\" src=\"https:\/\/kinsta.com\/wp-content\/uploads\/2023\/04\/react-card.jpg\" alt=\"\u30b7\u30f3\u30d7\u30eb\u306aReact\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\" width=\"1806\" height=\"678\"><figcaption id=\"caption-attachment-152317\" class=\"wp-caption-text\">\u30b7\u30f3\u30d7\u30eb\u306aReact\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8<\/figcaption><\/figure>\n<p><code>import<\/code>\u306f\u3001\u30c8\u30c3\u30d7\u30ec\u30d9\u30eb\u306e\u30e2\u30b8\u30e5\u30fc\u30eb\u3067\u306e\u307f\u4f7f\u7528\u3067\u304d\u308b\u3053\u3068\u306b\u6ce8\u610f\u3057\u3066\u304f\u3060\u3055\u3044\uff08\u95a2\u6570\u3084\u30af\u30e9\u30b9\u306a\u3069\u306e\u5185\u90e8\u3067\u306f\u4f7f\u7528\u3067\u304d\u307e\u305b\u3093\uff09\u3002<\/p>\n<p><code>import<\/code>\u3068<code>export<\/code>\u306b\u3064\u3044\u3066\u306e\u3088\u308a\u5305\u62ec\u7684\u306a\u8aac\u660e\u306b\u3064\u3044\u3066\u306f\u3001\u4ee5\u4e0b\u306e\u30ea\u30bd\u30fc\u30b9\u3082\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<ul>\n<li><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/export\" target=\"_blank\" rel=\"noopener noreferrer\">\u30a8\u30af\u30b9\u30dd\u30fc\u30c8<\/a> (mdn web docs)<\/li>\n<li><a href=\"https:\/\/developer.mozilla.org\/en-US\/docs\/Web\/JavaScript\/Reference\/Statements\/import\" target=\"_blank\" rel=\"noopener noreferrer\">\u30a4\u30f3\u30dd\u30fc\u30c8<\/a> (mdn web docs)<\/li>\n<li><a href=\"https:\/\/react.dev\/learn\/importing-and-exporting-components\" target=\"_blank\" rel=\"noopener noreferrer\">\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30a4\u30f3\u30dd\u30fc\u30c8\u3068\u30a8\u30af\u30b9\u30dd\u30fc\u30c8<\/a> (React dev)<\/li>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/36795819\/when-should-i-use-curly-braces-for-es6-import\/36796281\" target=\"_blank\" rel=\"noopener noreferrer\">ES6\u30a4\u30f3\u30dd\u30fc\u30c8\u3067\u306f\u3001\u3044\u3064\u4e2d\u62ec\u5f27\u3092\u4f7f\u7528\u3059\u3079\u304d\u304b<\/a> (Stack Overflow)<\/li>\n<\/ul>\n\n<h2>\u307e\u3068\u3081<\/h2>\n<p>React\u306f\u73fe\u5728<a href=\"https:\/\/kinsta.com\/jp\/blog\/javascript-libraries\/#reactjs\">\u6ce8\u76ee\u306eJavaScript\u30e9\u30a4\u30d6\u30e9\u30ea<\/a>\u3067\u3042\u308a\u3001<a href=\"https:\/\/kinsta.com\/blog\/frontend-developer\/\">\u30a6\u30a7\u30d6\u958b\u767a<\/a>\u306e\u4e16\u754c\u3067\u6700\u3082<a 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