{"id":13131,"date":"2021-02-08T12:29:11","date_gmt":"2021-02-08T03:29:11","guid":{"rendered":"http:\/\/www.code-magagine.com\/?p=13131"},"modified":"2023-09-06T07:45:41","modified_gmt":"2023-09-05T22:45:41","slug":"%e3%80%90react%e3%80%91%e3%80%8cmemo%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=13131","title":{"rendered":"\u3010React\u3011\u300cReact.memo\u300d\u306b\u3064\u3044\u3066"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">React.memo\u3068\u306f\uff1f<\/h2>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u7d50\u679c\u3092\u30e1\u30e2\u5316\u3059\u308bReact\u306eAPI\u3001React16.6\u304b\u3089\u5c0e\u5165\u3055\u308c\u307e\u3057\u305f\u3002\u3042\u304f\u307e\u3067props\u306e\u5909\u66f4\u306b\u5bfe\u3057\u3066\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u306e\u5224\u5b9a\u304c\u884c\u308f\u308c\u308b\u3060\u3051\u3067state\u3084useContext\u3067\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u304c\u66f4\u65b0\u3055\u308c\u305f\u5834\u5408\u306f\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u306e\u5bfe\u8c61\u306b\u306a\u308b\u306e\u3067\u6ce8\u610f\u3067\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u80cc\u666f<\/h2>\n\n\n\n<p>\u5143\u3005\u3001\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u306f<span class=\"s1\">\u300c<\/span>shouldComponentUpdate<span class=\"s1\">\u300d\u3084\u300c<\/span>PureComponent<span class=\"s1\">\u300d\u306a\u3069\u306b\u3088\u3063\u3066\u4e0d\u8981\u306a\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3092\u56de\u907f\u3059\u308b\u305f\u3081\u306e\u6a5f\u80fd\u304c\u3042\u308a\u307e\u3057\u305f\u304c\u3001\u95a2\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u306f\u5fc5\u305a\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u3066\u3057\u307e\u3046\u3088\u3046\u306b\u306a\u3063\u3066\u3044\u307e\u3057\u305f\u3002\u3057\u304b\u3057\u3001\u3053\u306eHooks\u306eReact16.6\u304b\u3089\u767b\u5834\u3057\u305f\u300cReact.memo\u300d\u306b\u3088\u3063\u3066<span style=\"color: #ff0000;\"><strong>\u300cshouldComponentUpdate\u300d\u3084\u300cPureComponent\u300d\u3068\u540c\u7b49\u306e\u3053\u3068\u304c\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3057\u305f\u3002<\/strong><\/span><\/span><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u30e1\u30ea\u30c3\u30c8<\/h2>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3092\u9632\u6b62\u3057\u3001\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u5411\u4e0a\u3055\u305b\u308b\u3053\u3068\u304c\u3067\u304d\u308b\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u7528\u9014<\/h2>\n\n\n\n<p>\u4e0b\u8a18\u306e\u3088\u3046\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u5bfe\u3057\u3066memo\u5316\u3059\u308b\u3068\u826f\u3044\u3002<\/p>\n\n\n\n<p>\u89aa\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3068\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u3042\u3063\u305f\u5834\u5408\u306b\u3001\u89aa\u306b\u5b50\u304c\u305f\u304f\u3055\u3093\u3076\u3089\u4e0b\u304c\u3063\u3066\u3044\u308b\u5834\u5408\u3067\u3001\u305d\u308c\u305e\u308c\u500b\u5225\u306b\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304cstate\u3092\u4fdd\u6301\u3057\u3066\u3044\u308b\u5834\u5408\u3002<\/p>\n\n\n\n<p>\u89aa\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u3042\u308b\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306estate\u3092\u66f4\u65b0\u3057\u3066\u3057\u307e\u3046\u3068\u4ed6\u306e\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306b\u307e\u3067\u5f71\u97ff\u3057\u3066\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u3066\u3057\u307e\u3044\u307e\u3059\u3002<span style=\"color: #ff0000;\"><strong>\u5404\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092memo\u5316\u3057\u3066\u304a\u304f\u3053\u3068\u3067\u5fc5\u8981\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u307f\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/strong><\/span><\/p>\n\n\n\n<p>Hooks\u3067\u3042\u308buseCallback\u3068\u4f75\u7528\u3059\u308b\u3053\u3068\u3067\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u4e0d\u8981\u306a\u518d\u63cf\u753b\u3092\u30b9\u30ad\u30c3\u30d7\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u6ce8\u610f\u70b9<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u63cf\u753b\u3055\u308c\u308b\u90fd\u5ea6props\u306e\u5024\u304c\u5909\u308f\u308b\u3088\u3046\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u306f\u4f7f\u308f\u306a\u3044\u3002<\/h3>\n\n\n\n<p>\u5c0f\u898f\u6a21\u306astate\u3057\u304b\u6301\u305f\u306a\u3044\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u5834\u5408\u306f\u3001\u9006\u306bmemo\u3092\u4f7f\u3046\u3068\u30e9\u30a4\u30d5\u30b5\u30a4\u30af\u30eb\u304c\u767a\u751f\u3059\u308b\u30b3\u30b9\u30c8\u304c\u304b\u304b\u308b\u3060\u3051\u3067\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u304c\u843d\u3061\u307e\u3059\u3002\u57fa\u672c\u7684\u306b\u3001props\u306e\u5024\u304c\u5909\u66f4\u304c\u306a\u3044\u306e\u306b\u63cf\u753b\u3092\u4f55\u5ea6\u3082\u3055\u308c\u308b\u3088\u3046\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u4f7f\u3046\u3068\u826f\u3044\u3067\u3057\u3087\u3046\u3002(\u30d5\u30a9\u30fc\u30e0\u306e\u30c6\u30ad\u30b9\u30c8\u30dc\u30c3\u30af\u30b9\u306a\u3069\uff09<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">props\u3067\u95a2\u6570\u3092\u6e21\u3059\u5834\u5408\u306f\u3001useCallback\u3092\u4f7f\u3046\u3053\u3068\u3002<\/h3>\n\n\n\n<p>\u305b\u3063\u304b\u304f\u3001React.memo\u3067\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u30e1\u30e2\u5316\u3057\u3066\u3082\u3001props\u3067\u5373\u6642\u95a2\u6570\u3092\u6e21\u3057\u3066\u3057\u307e\u3046\u3068\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u3066\u3057\u307e\u3046\u4ed5\u69d8\u306e\u3088\u3046\u3067\u3059\u3002\u305d\u306e\u5834\u5408\u306f\u3001\u95a2\u6570\u306fuseCallback\u3067\u30e9\u30c3\u30d7\u3057\u3066\u6e21\u3059\u3088\u3046\u306b\u3057\u307e\u3057\u3087\u3046\u3002\uff08\u306a\u304a\u3001\u30af\u30e9\u30b9\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8shouldComponentUpdate\u3067\u3044\u3046\u3068\u3053\u308d\u306ebind\u3092\u4f7f\u3063\u3066\u3044\u5bfe\u7b56\u3057\u3066\u3044\u305f\u306e\u3092\u3001\u95a2\u6570\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\uff0bHooks\u3067\u306e\u540c\u7b49\u306e\u5bfe\u7b56\u306e\u3088\u3046\u3067\u3059\u3002\uff09<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u5b9f\u88c5\u8a2d\u8a08\u306e\u65b9\u91dd<\/h2>\n\n\n\n<p>\u57fa\u672c\u7684\u306b\u3059\u3079\u3066\u306e\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306fmemo\u3067\u56f2\u3063\u3066\u3042\u3052\u308c\u3070\u3088\u3044\u3068\u601d\u3044\u307e\u3059\u3002\u305f\u3060\u3001memo\u81ea\u4f53\u306b\u3082\u591a\u5c11\u306e\u30b3\u30b9\u30c8\u306f\u304b\u304b\u308b\u306e\u3067\u3001\u7c92\u5ea6\u304c\u3081\u3061\u3083\u3081\u3061\u3083\u5c0f\u3055\u3044\u3088\u3046\u306a\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306f\u4f7f\u308f\u306a\u3044\u3068\u3044\u3046\u5224\u65ad\u3082\u53ef\u80fd\u3068\u3044\u3046\u611f\u3058\u3067\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u69cb\u6587<\/h2>\n\n\n\n<pre class=\"wp-block-preformatted\">React.memo(\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8,\u95a2\u6570);<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u5b9f\u88c5\u4f8b<\/h2>\n\n\n\n<p>\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306eprops\u3067\u3042\u308ba\u306e\u524d\u56de\u306eprops\u3068\u4eca\u56de\u306eprops\u3067\u5024\u3092\u6bd4\u8f03\u3057\u3066\u7b49\u4fa1\u3067\u3042\u308c\u3070\u518d\u63cf\u753b\u3057\u307e\u305b\u3093\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">const Hello = React.memo(\n  ({a}) =&gt; { return &lt;h1&gt;Hello {a}&lt;\/h1&gt;; }\n);<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c\u4e8c\u5f15\u6570<\/h2>\n\n\n\n<p>\u3042\u307e\u308a\u4f7f\u3046\u30b1\u30fc\u30b9\u306f\u591a\u304f\u306a\u3044\u3067\u3059\u304c\u3001\u57fa\u672c\u7684\u306b\u306f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306eprops\u306b\u5bfe\u3057\u3066\u6307\u5b9a\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u5185\u306e\u4e00\u90e8\u30d7\u30ed\u30d1\u30c6\u30a3\u306e\u5909\u66f4\u767a\u751f\u306e\u5834\u5408\u3067\u3082\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u305b\u305f\u3044\u5834\u5408\u306b\u4f7f\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>function areEqual(prevProps, nextProps) {\n  if(prevProps.count !== nextProps.count) {\n    return false; \/\/ \u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\n  } else {\n    return true; \/\/ \u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u767a\u751f\u306a\u3057\n  }\n  \/*\n  false\uff1a\u524d\u3068\u5f8c\u306eprops\u304c\u7570\u306a\u308b\u3002\n  true\uff1a\n\u524d\u3068\u5f8c\u306eprops\u304c\u540c\u3058\u3067\u3042\u308b\u3002\n  *\/\n}\n\nconst memoComponent = memo(\u30e1\u30e2\u5316\u3059\u308b\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8(count\u3068\u3044\u3046props\u3092\u6301\u3064),areaEqual)<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">Props\u304c\u306a\u304f\u3066\u3082\u30e1\u30e2\u5316\u3067\u304d\u308b\u3089\u3057\u3044\u3002<\/h2>\n\n\n\n<p>\u5225\u306bReact.memo\u306f\u5fc5\u305a\u3057\u3082props\u3092\u5b50\u306b\u6e21\u3057\u3066\u3044\u308b\u5834\u5408\u306b\u52d5\u304f\u308f\u3051\u3058\u3083\u306a\u3044\u3089\u3057\u3044\u3067\u3059\u3002\uff08\u3082\u3061\u308d\u3093\u89aa\u306fprops\u3092\u6301\u3063\u3066\u308b\u5fc5\u8981\u304c\u3042\u308b\u304b\u3068\u601d\u3044\u307e\u3059\u304c\u3002\uff09<\/p>\n\n\n\n<p><a href=\"https:\/\/zenn.dev\/irico\/articles\/acafb8bc7fb7f7\">https:\/\/zenn.dev\/irico\/articles\/acafb8bc7fb7f7<\/a><\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"React.memo\u3068\u306f\uff1f \u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u7d50\u679c\u3092\u30e1\u30e2\u5316\u3059\u308bReact\u306eAPI\u3001React16.6\u304b\u3089\u5c0e\u5165\u3055\u308c\u307e\u3057\u305f\u3002\u3042\u304f\u307e\u3067props\u306e\u5909\u66f4\u306b\u5bfe\u3057\u3066\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u306e\u5224\u5b9a\u304c\u884c\u308f\u308c\u308b\u3060\u3051\u3067state\u3084useCo [&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\/13131"}],"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=13131"}],"version-history":[{"count":16,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/13131\/revisions"}],"predecessor-version":[{"id":22438,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=\/wp\/v2\/posts\/13131\/revisions\/22438"}],"wp:attachment":[{"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13131"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.code-magagine.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}