{"id":13052,"date":"2021-01-24T14:21:49","date_gmt":"2021-01-24T05:21:49","guid":{"rendered":"http:\/\/www.code-magagine.com\/?p=13052"},"modified":"2023-09-04T23:41:01","modified_gmt":"2023-09-04T14:41:01","slug":"%e3%80%90react%e3%80%91%e3%80%8c%e3%83%a9%e3%82%a4%e3%83%95%e3%82%b5%e3%82%a4%e3%82%af%e3%83%ab%e3%80%8d%e3%82%84%e3%80%8c%e3%83%95%e3%83%83%e3%82%af%e3%80%8d%e3%81%ab%e3%81%a4%e3%81%84%e3%81%a6","status":"publish","type":"post","link":"http:\/\/www.code-magagine.com\/?p=13052","title":{"rendered":"\u3010React\u3011\u300c\u30e9\u30a4\u30d5\u30b5\u30a4\u30af\u30eb\u300d\u3084\u300c\u30d5\u30c3\u30af(Hooks)\u300d\u306b\u3064\u3044\u3066"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">\u30e9\u30a4\u30d5\u30b5\u30a4\u30af\u30eb\u3068\u306f\uff1f<\/h2>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u30de\u30a6\u30f3\u30c8\uff08\u63cf\u753b\uff09\u3055\u308c\u3066\u304b\u3089\u30a2\u30f3\u30de\u30a6\u30f3\u30c8\uff08\u7834\u68c4\uff09\u3055\u308c\u308b\u307e\u3067\u306e\u904e\u7a0b\u306e\u3053\u3068\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u30d5\u30a7\u30fc\u30ba<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">\u30de\u30a6\u30f3\u30c8<\/h4>\n\n\n\n<h4 class=\"wp-block-heading\">\u66f4\u65b0\uff08\u30de\u30a6\u30f3\u30c8\u3057\u305f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u66f4\u65b0\uff09<\/h4>\n\n\n\n<h4 class=\"wp-block-heading\">\u30a2\u30f3\u30de\u30a6\u30f3\u30c8<\/h4>\n\n\n\n<h2 class=\"wp-block-heading\">\u30d5\u30c3\u30af\u306e\u30eb\u30fc\u30eb<\/h2>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5916\u3067\u30d5\u30c3\u30af\u3092\u547c\u3073\u51fa\u3057\u3066\u306f\u3044\u3051\u306a\u3044\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u30d5\u30c3\u30af(Hook)\u3068\u306f\uff1f<\/h2>\n\n\n\n<p>\u95a2\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u5229\u7528\u3067\u304d\u308b\u95a2\u6570\u306e\u3053\u3068\u3067\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u30e1\u30ea\u30c3\u30c8<\/h3>\n\n\n\n<ul>\n<li>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5185\u3067\u91cd\u8907\u3059\u308b\u30ed\u30b8\u30c3\u30af\u3092\u30d5\u30c3\u30af\u3068\u3057\u3066\u5207\u308a\u51fa\u3059\u3053\u3068\u3067\u8907\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u5171\u901a\u5229\u7528\u3067\u304d\u308b\u3002<\/li>\n\n\n\n<li>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304b\u3089\u8907\u96d1\u306a\u30ed\u30b8\u30c3\u30af\u3092\u30d5\u30c3\u30af\u3068\u3057\u3066\u5207\u308a\u51fa\u305b\u3070\u30b3\u30fc\u30c9\u306e\u898b\u901a\u3057\u304c\u3088\u304f\u306a\u308b\u3002<\/li>\n\n\n\n<li>\u72b6\u614b\u7ba1\u7406\u3084\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u3092\u7c21\u6f54\u306b\u8a18\u8ff0\u3067\u304d\u308b\u3002<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u30ab\u30b9\u30bf\u30e0\u30d5\u30c3\u30af<\/h3>\n\n\n\n<p>\u81ea\u4f5c\u306e\u30d5\u30c3\u30af\u306e\u3053\u3068\u3067\u3059\u3002\u57fa\u672c\u7684\u306b\u30ab\u30b9\u30bf\u30e0\u30d5\u30c3\u30af\u5185\u3067\u95a2\u6570\u3092\u5b9a\u7fa9\u3059\u308b\u5834\u5408\u306f\u3001useCallback\u3092\u4f7f\u3046\u3053\u3068\u304c\u63a8\u5968\u3055\u308c\u307e\u3059\u3002\u3044\u308d\u3093\u306a\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u4f7f\u3046\u3053\u3068\u304c\u60f3\u5b9a\u3055\u308c\u308b\u306e\u3067\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7d44\u307f\u8fbc\u307e\u308c\u305f\u30d5\u30c3\u30af<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">useState<\/h4>\n\n\n\n<p>state\u3068state\u3092\u5b9a\u7fa9\u3084\u66f4\u65b0\u3059\u308b\u95a2\u6570\u3092\u8fd4\u3059\u30d5\u30c3\u30af\u3067\u3059\u3002\u3053\u308c\u3092\u4f7f\u3048\u3070\u95a2\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5185\u3067state\u7ba1\u7406\uff08\u5024\u306e\u4fdd\u6301\uff09\u3092\u884c\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">\u69cb\u6587<\/h5>\n\n\n\n<pre class=\"wp-block-preformatted\">const [State\u5909\u6570,State\u66f4\u65b0\u95a2\u6570] = useState(State\u5909\u6570\u306e\u521d\u671f\u5024);<\/pre>\n\n\n\n<p>state\u66f4\u65b0\u95a2\u6570\u306e\u540d\u524d\u306f\u5927\u62b5\u306e\u5834\u5408\u306f<span style=\"color: #ff0000;\"><strong>\u300csetXXX\u300d<\/strong><\/span>\u3068\u3044\u3046\u540d\u524d\u304c\u4ed8\u3051\u3089\u308c\u308b\u3053\u3068\u304c\u591a\u3044\u3067\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">\u5b9f\u88c5\u4f8b<\/h5>\n\n\n\n<p>\u30af\u30ea\u30c3\u30af\u3057\u305f\u3089\u30ab\u30a6\u30f3\u30c8\u30a2\u30c3\u30d7\u3055\u308c\u308bTest\u3068\u3044\u3046\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u4f8b<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">const { useState } = React;(import React,{useState} from 'react';\uff09\nconst [count,setCount] = useState(0);\n\nfunction Test(){\n  const [count,setCount] = useState(0);\n  return &lt;h1 onClick={()=&gt;setCount(count + 1)}&gt;Num:{count}&lt;\/h1&gt;;\n}<\/pre>\n\n\n\n<p>\u4e0b\u8a18\u306e\u3088\u3046\u306b\u3059\u308c\u3070State\u66f4\u65b0\u95a2\u6570\u306b\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570(c => c)\u3082\u6e21\u3059\u3053\u3068\u306f\u53ef\u80fd\u3067\u3059\u3002\u95a2\u6570\u3067\u6e21\u3057\u305f\u300cc\u300d\u306b\u306f\u73fe\u5728\u306ecount\u306e\u5024\u304c\u683c\u7d0d\u3055\u308c\u307e\u3059\u3002\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u306e\u623b\u308a\u5024\u304c\u6b21\u306e\u30b9\u30c6\u30fc\u30c8\u5185\u5bb9\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">const { useState } = React;\nfunction Test(){\n  const [count,setCount] = useState(0);\n  return &lt;h1 onClick={()=&gt;setCount( c =&gt; c + 1)}&gt;Count:{count}&lt;\/h1&gt;;\n}<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">useReducer<\/h4>\n\n\n\n<p>useState\u3068\u540c\u3058\u3088\u3046\u306b\u3001\u8907\u6570\u306e\u95a2\u9023\u3057\u305f\u30b9\u30c6\u30fc\u30c8\u3001\u3064\u307e\u308a\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u72b6\u614b\u3092\u4fdd\u6301\u3059\u308b\u969b\u306b\u4f7f\u3046\u3068\u826f\u3044\u3067\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">useState\u3068\u306e\u9055\u3044\u3001\u30e1\u30ea\u30c3\u30c8<\/h5>\n\n\n\n<p>\u4f8b\u3048\u3070\u3001API\u3092\u5b9f\u884c\u3057\u3066\u51e6\u7406\u7d50\u679c\u3092\u66f4\u65b0\u3059\u308b\u969b\u306a\u3069\u306f\u3001useState\u3060\u3068onClick\u306b\u30ed\u30b8\u30c3\u30af\u304c\u5bc4\u3063\u3066\u3057\u307e\u3044\u304c\u3061\u306b\u306a\u308a\u307e\u3059\u304c\u3001useReducer\u3092\u4f7f\u3046\u3053\u3068\u3067\u5916\u90e8\u5316\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u307e\u305f\u3001\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3092\u8a18\u8ff0\u3059\u308b\u969b\u306b\u30ed\u30b8\u30c3\u30af\u3068\u758e\u7d50\u5408\u306b\u306a\u308a\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30c6\u30b9\u30c8\u3092\u66f8\u304f\u306e\u304c\u697d\u306b\u306a\u308a\u307e\u3059\u3002\uff08Reducer\u306f\u72b6\u614b\u3092\u6301\u305f\u306a\u3044\u95a2\u6570\u306a\u306e\u3067\u30c6\u30b9\u30c8\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u306e\u304c\u7c21\u5358\u306b\u306a\u308a\u307e\u3059\u3002\uff09<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">useEffect<\/h4>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u526f\u4f5c\u7528\u3092\u8ffd\u52a0\u3059\u308b\u30d5\u30c3\u30af\u3067\u3059\u3002\u526f\u4f5c\u7528\u3068\u306f\u6b21\u306e\u3088\u3046\u306a\u51e6\u7406\u3092\u5b9f\u884c\u3059\u308b\u95a2\u6570\u306e\u3053\u3068\u3002\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30de\u30a6\u30f3\u30c8\u5f8c\u306b\u6307\u5b9a\u3057\u305f\u526f\u4f5c\u7528\u3092\u5b9f\u884c\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002<\/p>\n\n\n\n<ul>\n<li>DOM\u306e\u5909\u66f4<\/li>\n\n\n\n<li>API\u3068\u306e\u901a\u4fe1<\/li>\n\n\n\n<li>\u975e\u540c\u671f\u51e6\u7406<\/li>\n\n\n\n<li>console.log<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">\u52d5\u4f5c\u30bf\u30a4\u30df\u30f3\u30b0<\/h5>\n\n\n\n<p>\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u306e\u5f8c\u3067\u3059\u3002\u5f93\u6765\u306e\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u3044\u3046\u3068\u3053\u308d\u306e\u300c<em>componentDidMount<\/em>()\u300d\u306e\u52d5\u4f5c\u306b\u3088\u304f\u4f3c\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">\u69cb\u6587<\/h5>\n\n\n\n<p>\u7b2c\u4e00\u5f15\u6570\u306b\u526f\u4f5c\u7528\uff08\u95a2\u6570\u306a\u3069\uff09\u3092\u6e21\u305b\u3070\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30de\u30a6\u30f3\u30c8\u5f8c\u306b\u305d\u308c\u304c\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">useEffect(\u526f\u4f5c\u7528,[\u5909\u6570]);<\/pre>\n\n\n\n<p>\u7b2c\u4e8c\u5f15\u6570\u306b\u306f\u5909\u5316\u3092\u691c\u77e5\u3059\u308b\u5bfe\u8c61\u306e\u5909\u6570\u3092\u6307\u5b9a\u3057\u307e\u3059\u3002\uff08\u305d\u306e\u5909\u5316\u306e\u307f\u3067\u3057\u304b\u5b9f\u884c\u3055\u308c\u306a\u3044\u3088\u3046\u306b\u3067\u304d\u307e\u3059\u3002\uff09\u306a\u304a\u3001\u7b2c\u4e8c\u5f15\u6570\u306b\u7a7a\u306e\u914d\u5217\u3092\u6e21\u3059\u3053\u3068\u3067\u30de\u30a6\u30f3\u30c8\u5f8c1\u5ea6\u306e\u307fuseEffect\u3092\u5b9f\u884c\u3055\u305b\u308b\u3068\u3044\u3063\u305f\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">\u5b9f\u88c5\u4f8b<\/h5>\n\n\n\n<p>useEffect\u306bDOM\u3092\u63cf\u753b\u3059\u308b\u95a2\u6570\u3092\u6e21\u3057\u3066\u30de\u30a6\u30f3\u30c8\u5f8c\u306b\u518d\u63cf\u753b\u3092\u4f55\u5ea6\u3082\u884c\u308f\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">import React,{useState,useEffect} from'react';\n\nfunction App() {\n  const [count,setCount] = useState(0);\n\n  useEffect(()=&gt;{\n    document.getElementById('effect').innerText=`\u3042\u306a\u305f\u306f ${count}\u56de\u30af\u30ea\u30c3\u30af\u3057\u307e\u3057\u305f\u3002`;\n  });  \n\n  return(\n    &lt;div&gt;&lt;p id=\"effect\"&gt;&lt;\/p&gt;\n    &lt;button onClick={()=&gt;setCount(count+1)}&gt;click&lt;\/button&gt;&lt;\/div&gt;\n  );\n}<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\">useMemo\/useCallback<\/h4>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u5411\u4e0a\u306b\u4f7f\u3048\u307e\u3059\u3002\u5c11\u3057\u3084\u3084\u3053\u3057\u3044\u306e\u3067\u4e0b\u8a18\u306e\u8a18\u4e8b\u3067\u89e3\u8aac\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<p><blockquote class=\"wp-embedded-content\" data-secret=\"Vckzqa4qsD\"><a href=\"http:\/\/www.code-magagine.com\/?p=13735\">\u3010React\u3011\u300cuseMemo\/useCallback\u300d\u306b\u3064\u3044\u3066<\/a><\/blockquote><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;\u3010React\u3011\u300cuseMemo\/useCallback\u300d\u306b\u3064\u3044\u3066&#8221; &#8212; \u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u30de\u30ac\u30b8\u30f3\" src=\"http:\/\/www.code-magagine.com\/?p=13735&#038;embed=true#?secret=1f02aY2fJs#?secret=Vckzqa4qsD\" data-secret=\"Vckzqa4qsD\" width=\"500\" height=\"282\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">useContext<\/h4>\n\n\n\n<p>React\u306ehook\u306e\u4e00\u3064\u3067\u3059\u3002\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u9593\u306e\u30b9\u30c6\u30fc\u30c8\u306e\u5171\u6709\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u30aa\u30d6\u30b8\u30a7\u30af\u30c8(React.createContext\u306e\u623b\u308a\u5024\uff09\u304b\u3089\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306e\u5024\u3092\u53d6\u5f97\u3059\u308b\u30d5\u30c3\u30af\u3067\u3059\u3002Props\u3092\u5229\u7528\u3057\u306a\u304f\u3066\u3082\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u30c7\u30fc\u30bf\u3092\u6e21\u305b\u307e\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">Context\u30aa\u30d6\u30b8\u30a7\u30af\u30c8<\/h5>\n\n\n\n<p>\u89aa\u5b50\u95a2\u4fc2\u306b\u306a\u3044\u96e2\u308c\u305f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u9593\u3067\u5171\u6709\u3059\u308b\u305f\u3081\u306e\u30d1\u30fc\u30c4\u3067\u3059\u3002Context\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u306f\u300cContext Provider\u300d\u3068\u300cContext Consumer\u300d\u306e2\u7a2e\u985e\u306e\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h6 class=\"wp-block-heading\">Context Provider<\/h6>\n\n\n\n<p>\u30c4\u30ea\u30fc\u306e\u30c8\u30c3\u30d7\u306b\u6307\u5b9a\u3059\u308b\u3053\u3068\u3067Context\u3092\u53c2\u7167\u3067\u304d\u308b\u7bc4\u56f2\u3092\u9650\u5b9a\u3059\u308b\u305f\u3081\u306b\u4f7f\u7528\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h6 class=\"wp-block-heading\">Context Consumer<\/h6>\n\n\n\n<p>Context\u306e\u5024\u3092\u5229\u7528\u3057\u305f\u3044\u5834\u6240\u3067\u4f7f\u7528\u3057\u307e\u3059\u3002\u306a\u304a\u3001React Hook\u306e<span style=\"color: #ff0000;\"><strong>\u300cuseContext\u300d<\/strong><\/span>\u306fConsumer\u306e\u4ee3\u66ff\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">useState\u3084useReducer\u3068\u306e\u9055\u3044<\/h5>\n\n\n\n<p>useState\u3084useReducer\u3067\u3082\u30b9\u30c6\u30fc\u30c8\u306e\u5171\u6709\u306f\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u304b\u3068\u601d\u3044\u307e\u3059\u3002\u9055\u3044\u3068\u3057\u3066\u306f<span style=\"color: #ff0000;\"><strong>props\u3067\u306e\u30d0\u30b1\u30c4\u30ea\u30ec\u30fc\u304c\u767a\u751f\u3057\u306a\u3044\u70b9<\/strong><\/span>\u3067\u3059\u3002<\/p>\n\n\n\n<h6 class=\"wp-block-heading\">\u7528\u9014<\/h6>\n\n\n\n<p>\u4e0b\u8a18\u306e\u3088\u3046\u306a\u30b5\u30a4\u30c8\u3092\u901a\u3058\u3066\u6c4e\u7528\u6027\u306e\u3042\u308b\u60c5\u5831\u3092\u5171\u6709\u3057\u305f\u3044\u5834\u5408\u306a\u3069\u306b\u4f7f\u3048\u307e\u3059\u3002<\/p>\n\n\n\n<ul>\n<li>\u8a8d\u8a3c\u72b6\u614b<\/li>\n\n\n\n<li>\u30ec\u30a4\u30a2\u30a6\u30c8\u306e\u30c7\u30b6\u30a4\u30f3\u60c5\u5831<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">\u5b9f\u88c5\u4f8b<\/h5>\n\n\n\n<pre class=\"wp-block-preformatted\">import React,{useState,useContext,createContext} from'react';\n\nconst MyContext = createContext();\n\nfunction App() {\n  const [count,setCount] = useState(0);\n  const value = { name:'soarflat',\n                  handleClick:()=&gt;setCount(count=&gt;count+1)};\n  return(\n    &lt;div&gt;\n      &lt;p&gt;count:{count}&lt;\/p&gt;\n      &lt;MyContext.Provider value={value}&gt;\n        &lt;ChildComponent\/&gt;\n      &lt;\/MyContext.Provider&gt;\n    &lt;\/div&gt;\n  );\n}\n\nfunction ChildComponent(){\n  return &lt;GrandChildComponent\/&gt;;\n}\n\nfunction GrandChildComponent(){\n  const context = useContext(MyContext);\n\n  return(\n    &lt;&gt;\n      &lt;p&gt;{context.name}&lt;\/p&gt;\n      &lt;button onClick={context.handleClick}&gt;increment&lt;\/button&gt;\n    &lt;\/&gt;\n  );\n}\n\nexport default App;\n<\/pre>\n\n\n\n<p>props\u306e\u30d0\u30b1\u30c4\u30ea\u30ec\u30fc\u3092\u3059\u308b\u3053\u3068\u306a\u304f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u9593\u3067\u5024\u3092\u6e21\u3059\u3053\u3068\u304c\u3067\u304d\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">useRef<\/h4>\n\n\n\n<p>ref\u30aa\u30d6\u30b8\u30a7\u30af\u30c8(React.createRef\u306e\u623b\u308a\u5024\uff09\u3092\u8fd4\u3059\u30d5\u30c3\u30af\u3067\u3059\u3002ref\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u5229\u7528\u3059\u308b\u3053\u3068\u3067DOM\u306e\u53c2\u7167\u3084\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5185\u3067\u524d\u56de\u306estate\u3092\u4fdd\u6301\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002<\/p>\n\n\n\n<h5 class=\"wp-block-heading\">\u69cb\u6587<\/h5>\n\n\n\n<p>ref\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u751f\u6210\u3067\u304d\u307e\u3059\u3002ref\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092HTML\u306eref\u5c5e\u6027\u306b\u6307\u5b9a\u3059\u308b\u3053\u3068\u3067DOM\u3092\u53c2\u7167\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">useRef(\u5024)\n\nconst \u5909\u6570 = useRef(\u5024);\n\u5909\u6570.current \/\/useRef\u3067\u6307\u5b9a\u3057\u305f\u5024\u3092\u53c2\u7167\u3067\u304d\u307e\u3059\u3002<\/pre>\n\n\n\n<h5 class=\"wp-block-heading\">\u5b9f\u88c5\u4f8b<\/h5>\n\n\n\n<pre class=\"wp-block-preformatted\">import React,{useRef} from'react';\n\nfunction App(){ \n  const useref = useRef(null);\n  const onButtonClick=()=&gt;{\n    if(!useref.current) return;\n    useref.current.focus();\n  };\n\n  return(\n    &lt;&gt;\n      &lt;input ref={useref} type=\"text\"\/&gt;\n      &lt;button onClick={onButtonClick}&gt;input\u8981\u7d20\u3092\u30d5\u30a9\u30fc\u30ab\u30b9\u3059\u308b&lt;\/button&gt;\n    &lt;\/&gt;\n  );\n}\n\nexport default App;<\/pre>\n","protected":false},"excerpt":{"rendered":"\u30e9\u30a4\u30d5\u30b5\u30a4\u30af\u30eb\u3068\u306f\uff1f 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[&hellip;]","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[116],"tags":[],"_links":{"self":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/13052"}],"collection":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=13052"}],"version-history":[{"count":20,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/13052\/revisions"}],"predecessor-version":[{"id":22405,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/13052\/revisions\/22405"}],"wp:attachment":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13052"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13052"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13052"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}