{"id":1219,"date":"2025-04-13T16:04:46","date_gmt":"2025-04-13T07:04:46","guid":{"rendered":"https:\/\/route-zero.com\/recruit\/route\/1219\/"},"modified":"2025-05-22T18:55:45","modified_gmt":"2025-05-22T09:55:45","slug":"1219","status":"publish","type":"route","link":"https:\/\/route-zero.com\/recruit\/route\/1219\/","title":{"rendered":"\u3010\u5b8c\u5168\u7248\u3011\u578b\u306e\u5909\u63db\u3068\u306f\uff1f\u30ad\u30e3\u30b9\u30c8\u306e\u57fa\u672c\u3068\u843d\u3068\u3057\u7a74\u300d | Java\u30fbJavaScript\u30fbTypeScript\u3067\u5fb9\u5e95\u7406\u89e3\u3059\u308b\u578b\u306e\u6271\u3044\u65b9"},"content":{"rendered":"<div>\n<h2>\u306a\u305c\u300c\u578b\u306e\u5909\u63db\u300d\u3092\u7406\u89e3\u3059\u3079\u304d\u304b\uff1f<\/h2>\n<p>\u307f\u306a\u3055\u3093\u306f\u3001\u3053\u3093\u306a\u7d4c\u9a13\u3092\u3057\u305f\u3053\u3068\u3042\u308a\u307e\u305b\u3093\u304b\uff1f<\/p>\n<ul>\n<li>\n<p>\u6570\u5024\u3068\u3057\u3066\u52a0\u7b97\u3057\u305f\u3064\u3082\u308a\u304c\u6587\u5b57\u5217\u3068\u3057\u3066\u7d50\u5408\u3055\u308c\u3066\u3044\u305f<\/p>\n<\/li>\n<li>\n<p>API\u306e\u623b\u308a\u5024\u3092\u51e6\u7406\u3057\u305f\u3089\u3001\u60f3\u5b9a\u5916\u306e\u30a8\u30e9\u30fc\u304c\u51fa\u305f<\/p>\n<\/li>\n<li>\n<p>\u578b\u3092\u30ad\u30e3\u30b9\u30c8\u3057\u305f\u306f\u305a\u306a\u306e\u306b\u3001\u5b9f\u884c\u6642\u306b\u30af\u30e9\u30c3\u30b7\u30e5\u3057\u305f<\/p>\n<\/li>\n<\/ul>\n<p>\u3053\u308c\u3089\u306f\u3059\u3079\u3066\u300c\u578b\u306e\u6271\u3044\u300d\u3084\u300c\u578b\u5909\u63db\u300d\u306b\u3088\u308b\u554f\u984c\u3067\u3059\u3002<br \/>\u578b\u5909\u63db\uff08\u30ad\u30e3\u30b9\u30c8\uff09\u306f\u3001\u8a00\u8a9e\u3054\u3068\u306b\u30eb\u30fc\u30eb\u304c\u7570\u306a\u308a\u3001\u77e5\u3089\u306a\u3044\u3068\u3059\u3050\u306b\u843d\u3068\u3057\u7a74\u306b\u306f\u307e\u3063\u3066\u3057\u307e\u3044\u307e\u3059\u3002<br \/>\u672c\u8a18\u4e8b\u3067\u306f\u3001<strong>Java\u30fbJavaScript\u30fbTypeScript\u306e3\u8a00\u8a9e\u3092\u4f7f\u3063\u3066\u3001\u578b\u306e\u5909\u63db\u3068\u305d\u306e\u6b63\u3057\u3044\u4f7f\u3044\u65b9\u3092\u308f\u304b\u308a\u3084\u3059\u304f\u5fb9\u5e95\u89e3\u8aac<\/strong>\u3057\u307e\u3059\u3002<\/p>\n<hr>\n<h2>\u578b\u5909\u63db\u306e\u57fa\u672c\u3068\u5404\u8a00\u8a9e\u3067\u306e\u5b9f\u88c5<\/h2>\n<h2>JavaScript\uff1a\u67d4\u8edf\u3059\u304e\u308b\u578b\u5909\u63db\u306b\u8981\u6ce8\u610f<\/h2>\n<h3>\u4f8b1\uff1a&#8221;5&#8243; + 1 \u2192 &#8220;51&#8221;<\/h3>\n<pre><code><span>console<\/span>.log(<span>\"5\"<\/span> + <span>1<\/span>); <span>\/\/ \u2192 \"51\"<\/span><\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>+ \u6f14\u7b97\u5b50\u306f\u6570\u5024\u540c\u58eb\u306a\u3089\u52a0\u7b97\u3092\u884c\u3044\u307e\u3059\u304c\u3001\u3069\u3061\u3089\u304b\u304c\u6587\u5b57\u5217\u3067\u3042\u308c\u3070\u300c\u6587\u5b57\u5217\u9023\u7d50\u300d\u306b\u5909\u308f\u308a\u307e\u3059\u3002\u3053\u306e\u30b3\u30fc\u30c9\u3067\u306f &#8220;5&#8221; \u304c\u6587\u5b57\u5217\u306a\u306e\u3067\u30011 \u306f\u81ea\u52d5\u7684\u306b &#8220;1&#8221; \u306b\u5909\u63db\u3055\u308c\u3001\u7d50\u679c\u306f &#8220;51&#8221; \u306b\u306a\u308a\u307e\u3059\u3002JavaScript\u3067\u306f\u6697\u9ed9\u7684\u306a\u578b\u5909\u63db\uff08implicit coercion\uff09\u304c\u591a\u304f\u3001\u3053\u308c\u304c\u539f\u56e0\u3067\u610f\u56f3\u3057\u306a\u3044\u30d0\u30b0\u3092\u751f\u3080\u3053\u3068\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1a+ \u306f\u300c\u6587\u5b57\u5217\u512a\u5148\u300d\u306a\u306e\u3067\u3001\u6df7\u5728\u3059\u308b\u578b\u306e\u6f14\u7b97\u3067\u306f\u6ce8\u610f\uff01<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u6570\u5024\u52a0\u7b97\u306e\u3064\u3082\u308a\u3067\u6587\u5b57\u5217\u9023\u7d50\u306b\u306a\u308b\u3068\u3001\u8a08\u7b97\u30ed\u30b8\u30c3\u30af\u304c\u7834\u7dbb\u3057\u307e\u3059\u3002<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b2\uff1a&#8221;5&#8243; &#8211; 1 \u2192 4<\/h3>\n<pre><code><span>console<\/span>.log(<span>\"5\"<\/span> - <span>1<\/span>); <span>\/\/ \u2192 4<\/span><\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f &#8211; \u6f14\u7b97\u5b50\u304c\u4f7f\u308f\u308c\u3066\u3044\u307e\u3059\u304c\u3001- \u306f\u6570\u5024\u6f14\u7b97\u306e\u307f\u3092\u884c\u3044\u307e\u3059\u3002\u305d\u306e\u305f\u3081\u3001JavaScript\u306f &#8220;5&#8221; \u3092<strong>\u6697\u9ed9\u7684\u306b\u6570\u5024\u3078\u5909\u63db<\/strong>\u3057\u3001\u7d50\u679c\u3068\u3057\u3066 5 &#8211; 1 = 4 \u306b\u306a\u308a\u307e\u3059\u3002\u3053\u306e\u3088\u3046\u306b\u3001\u6f14\u7b97\u5b50\u306b\u3088\u3063\u3066\u578b\u5909\u63db\u306e\u30eb\u30fc\u30eb\u304c\u5909\u308f\u308b\u306e\u304cJavaScript\u306e\u5384\u4ecb\u306a\u3068\u3053\u308d\u3067\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1a-, *, \/ \u306f\u5e38\u306b\u6570\u5024\u6f14\u7b97\u3002\u6587\u5b57\u5217\u3082\u6570\u5024\u306b\u5909\u63db\u3055\u308c\u308b\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u6587\u5b57\u5217\u306b\u6570\u5024\u4ee5\u5916\u306e\u6587\u5b57\u304c\u542b\u307e\u308c\u308b\u3068 NaN \u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b3\uff1aNumber(&#8220;42&#8221;) \u2192 42<\/h3>\n<pre><code><span>let<\/span> <span>str<\/span> = <span>\"42\"<\/span>;\r\n<span>let<\/span> num = Number(<span>str<\/span>); <span>\/\/ \u2192 42<\/span><\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f\u3001\u660e\u793a\u7684\u306a\u578b\u5909\u63db\uff08explicit conversion\uff09\u3068\u3057\u3066 Number() \u95a2\u6570\u3092\u4f7f\u3063\u3066\u3044\u307e\u3059\u3002&#8221;42&#8243; \u306f\u6570\u5024\u306e\u5f62\u3092\u3057\u3066\u3044\u308b\u306e\u3067\u3001Number(&#8220;42&#8221;) \u306f 42 \u3068\u3044\u3046\u6570\u5024\u306b\u306a\u308a\u307e\u3059\u3002<strong>\u660e\u793a\u7684\u306b\u578b\u5909\u63db\u3059\u308b\u3053\u3068\u3067\u3001\u610f\u56f3\u3057\u306a\u3044\u6319\u52d5\u3092\u9632\u304e\u3001\u30b3\u30fc\u30c9\u306e\u53ef\u8aad\u6027\u3068\u4fdd\u5b88\u6027\u304c\u5411\u4e0a<\/strong>\u3057\u307e\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1a\u6697\u9ed9\u5909\u63db\u3092\u907f\u3051\u3001\u660e\u793a\u7684\u306b Number(), String() \u3092\u4f7f\u3046\u3053\u3068\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u5909\u63db\u3067\u304d\u306a\u3044\u6587\u5b57\u5217\uff08\u4f8b\uff1a&#8221;abc&#8221;\uff09\u306f NaN \u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b4\uff1aBoolean(&#8220;0&#8221;) \u2192 true<\/h3>\n<pre><code><span>console<\/span>.log(<span>Boolean<\/span>(<span>\"0\"<\/span>)); <span>\/\/ \u2192 true<\/span><\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>JavaScript\u3067\u306f\u3001\u7a7a\u6587\u5b57\u5217 &#8220;&#8221; \u3084 0 \u306f false \u3068\u3057\u3066\u6271\u308f\u308c\u307e\u3059\u304c\u3001&#8221;0&#8243;\uff08\u6587\u5b57\u5217\u306e\u30bc\u30ed\uff09\u306f\u300c\u7a7a\u3067\u306f\u306a\u3044\u6587\u5b57\u5217\u300d\u306a\u306e\u3067 true \u306b\u306a\u308a\u307e\u3059\u3002\u3053\u3053\u3067\u306e\u843d\u3068\u3057\u7a74\u306f\u3001<strong>\u76f4\u611f\u7684\u306b\u306f 0 \u2192 false \u3068\u8003\u3048\u305f\u304f\u306a\u308b<\/strong>\u70b9\u3067\u3059\u3002\u6587\u5b57\u5217 &#8220;false&#8221; \u3067\u3059\u3089\u771f\u3068\u8a55\u4fa1\u3055\u308c\u308b\u306e\u3067\u3001\u53b3\u5bc6\u306a\u30c1\u30a7\u30c3\u30af\u304c\u6c42\u3081\u3089\u308c\u307e\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1aBoolean(value) \u3067\u5909\u63db\u3055\u308c\u308b\u57fa\u6e96\u3092\u77e5\u308b<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a&#8221;0&#8243;, &#8220;false&#8221; \u3082\u771f\uff08truthy\uff09\u3068\u3057\u3066\u8a55\u4fa1\u3055\u308c\u308b\uff01<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h2>Java\uff1a\u30ad\u30e3\u30b9\u30c8\u3068\u4f8b\u5916\u306b\u8981\u6ce8\u610f<\/h2>\n<h3>\u4f8b1\uff1a(int) 3.99 \u2192 3<\/h3>\n<pre><code><span>double<\/span> d = <span>3.99<\/span>;\r\n<span>int<\/span> i = (<span>int<\/span>) d;<\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u306f\u300c\u7cbe\u5ea6\u3092\u4e0b\u3052\u308b\u65b9\u5411\u3078\u306e\u5909\u63db\uff08Narrowing conversion\uff09\u300d\u3067\u3001Java\u3067\u306f\u660e\u793a\u7684\u306a\u30ad\u30e3\u30b9\u30c8\u304c\u5fc5\u8981\u3067\u3059\u3002double \u304b\u3089 int \u3078\u5909\u63db\u3059\u308b\u3068\u3001\u5c0f\u6570\u70b9\u4ee5\u4e0b\u306f\u5207\u308a\u6368\u3066\u3089\u308c\u307e\u3059\u3002<strong>\u610f\u56f3\u7684\u306a\u30ad\u30e3\u30b9\u30c8\u3067\u3042\u3063\u3066\u3082\u3001\u7cbe\u5ea6\u304c\u843d\u3061\u308b\u3053\u3068\u306f\u4ed5\u69d8\u306a\u306e\u3067\u3001\u6ce8\u610f\u304c\u5fc5\u8981\u3067\u3059\u3002<\/strong><\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1aNarrowing\uff08\u7cbe\u5ea6\u3092\u4e0b\u3052\u308b\uff09\u306b\u306f\u5fc5\u305a\u30ad\u30e3\u30b9\u30c8 (int) \u304c\u5fc5\u8981<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u5c0f\u6570\u70b9\u306f\u5207\u308a\u6368\u3066\uff08\u56db\u6368\u4e94\u5165\u3067\u306f\u306a\u3044\uff09<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b2\uff1aInteger.parseInt(&#8220;123&#8221;) \u2192 123<\/h3>\n<pre><code>String input = <span>\"123\"<\/span>;\r\n<span>int<\/span> <span>value<\/span> = Integer.parseInt(input);<\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f\u6587\u5b57\u5217\u304b\u3089\u6574\u6570\u3078\u306e\u5909\u63db\u3092\u884c\u3063\u3066\u3044\u307e\u3059\u3002Java\u3067\u306f\u3001parseInt() \u3092\u4f7f\u3063\u3066\u6587\u5b57\u5217\u3092\u6570\u5024\u306b\u5909\u63db\u3067\u304d\u307e\u3059\u3002\u305f\u3060\u3057\u3001\u5909\u63db\u5bfe\u8c61\u306e\u6587\u5b57\u5217\u304c\u6570\u5024\u3067\u306a\u3044\u3068 NumberFormatException \u304c\u767a\u751f\u3059\u308b\u305f\u3081\u3001<strong>\u4e8b\u524d\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u304c\u91cd\u8981<\/strong>\u3067\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1a\u6587\u5b57\u5217\u304b\u3089\u6570\u5024\u3078\u306e\u5909\u63db\u306b\u306f parseInt(), parseDouble() \u3092\u4f7f\u3046<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u4e0d\u6b63\u306a\u6587\u5b57\u5217\uff08\u4f8b\uff1a&#8221;abc&#8221;\uff09\u306f\u4f8b\u5916\u3092\u30b9\u30ed\u30fc\u3057\u307e\u3059<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b3\uff1a(String) obj \u2192 ClassCastException<\/h3>\n<pre><code><span>Object<\/span> obj = <span>42<\/span>;\r\n<span>String<\/span> s = (<span>String<\/span>) obj; <span>\/\/ \u5b9f\u884c\u6642\u4f8b\u5916<\/span><\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f\u3001Object \u578b\u304b\u3089 String \u578b\u3078\u30ad\u30e3\u30b9\u30c8\u3057\u3088\u3046\u3068\u3057\u3066\u3044\u307e\u3059\u304c\u3001\u5b9f\u4f53\u304c Integer \u3067\u3042\u308b\u305f\u3081 ClassCastException \u304c\u767a\u751f\u3057\u307e\u3059\u3002<strong>Java\u306e\u30ad\u30e3\u30b9\u30c8\u306f\u300c\u898b\u304b\u3051\u306e\u578b\u300d\u3060\u3051\u3067\u306f\u306a\u304f\u3001\u5b9f\u4f53\u578b\u3082\u4e00\u81f4\u3057\u3066\u3044\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044<\/strong>\u70b9\u304c\u975e\u5e38\u306b\u91cd\u8981\u3067\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1a\u30ad\u30e3\u30b9\u30c8\u524d\u306b\u306f instanceof \u3092\u4f7f\u3063\u3066\u5b9f\u4f53\u3092\u78ba\u8a8d<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u8aa4\u3063\u305f\u30ad\u30e3\u30b9\u30c8\u306f<strong>\u5b9f\u884c\u6642\u4f8b\u5916<\/strong>\u3067\u843d\u3061\u307e\u3059\uff08\u30b3\u30f3\u30d1\u30a4\u30eb\u306f\u901a\u308b\uff09<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h2>TypeScript\uff1a\u578b\u5b89\u5168\u3068\u30ad\u30e3\u30b9\u30c8\u306e\u4e21\u7acb\u304c\u30ab\u30ae<\/h2>\n<h3>\u4f8b1\uff1a(value as string).length<\/h3>\n<pre><code><span>let<\/span> <span>value<\/span>: any = <span>\"hello\"<\/span>;\r\n<span>let<\/span> len = (<span>value<\/span> <span>as<\/span> <span>string<\/span>).length;<\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f\u3001value \u306e\u578b\u304c any \u3067\u3042\u308b\u305f\u3081\u3001TypeScript\u5074\u3067\u306f\u578b\u60c5\u5831\u304c\u4e0d\u660e\u3067\u3059\u3002\u305d\u306e\u305f\u3081\u3001\u958b\u767a\u8005\u304c\u300c\u3053\u308c\u306f string \u3067\u3042\u308b\u300d\u3068\u660e\u793a\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u308c\u3092 <strong>\u578b\u30a2\u30b5\u30fc\u30b7\u30e7\u30f3\uff08\u578b\u30ad\u30e3\u30b9\u30c8\uff09<\/strong> \u3068\u547c\u3073\u307e\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u88dc\u5b8c\u3084\u30a8\u30e9\u30fc\u9632\u6b62\u304c\u52b9\u304f\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1aany \u306e\u5024\u3092\u6271\u3046\u3068\u304d\u306f\u578b\u30a2\u30b5\u30fc\u30b7\u30e7\u30f3\u3067\u88dc\u5f37<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1a\u5b9f\u969b\u306e\u578b\u304c\u9055\u3063\u3066\u3044\u308b\u3068\u5b9f\u884c\u6642\u30d0\u30b0\u306b\u3064\u306a\u304c\u308b<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b2\uff1aDOM\u64cd\u4f5c\u306e\u30ad\u30e3\u30b9\u30c8<\/h3>\n<pre><code><span>const<\/span> input = <span>document<\/span>.querySelector(<span>\"#email\"<\/span>) <span>as<\/span> HTMLInputElement;\r\n<span>console<\/span>.log(input.value);<\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>TypeScript\u3067 querySelector \u3092\u4f7f\u3046\u3068\u3001\u8fd4\u308a\u5024\u306f Element | null \u578b\u306b\u306a\u308a\u307e\u3059\u3002\u305d\u306e\u305f\u3081\u3001HTMLInputElement \u3067\u3042\u308b\u3053\u3068\u3092\u660e\u793a\u3059\u308b\u3053\u3068\u3067\u3001.value \u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u6b63\u3057\u304f\u5229\u7528\u3067\u304d\u307e\u3059\u3002<strong>\u30ad\u30e3\u30b9\u30c8\u3092\u4f7f\u308f\u306a\u3044\u3068\u88dc\u5b8c\u3082\u52b9\u304b\u305a\u3001\u578b\u30a8\u30e9\u30fc\u306b\u3082\u306a\u308a\u307e\u3059\u3002<\/strong><\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1aDOM\u8981\u7d20\u306e\u53d6\u5f97\u5f8c\u306f\u660e\u793a\u7684\u306b\u8981\u7d20\u578b\u3092\u30ad\u30e3\u30b9\u30c8\u3059\u308b<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1anull \u304b\u3082\u3057\u308c\u306a\u3044\u306e\u3067\u3001\u30ad\u30e3\u30b9\u30c8\u5f8c\u306b null \u30c1\u30a7\u30c3\u30af\u3092\u5165\u308c\u308b\u306e\u304c\u7406\u60f3<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h3>\u4f8b3\uff1aUnion\u578b\uff0b\u578b\u30ac\u30fc\u30c9<\/h3>\n<pre><code><span>type<\/span> Dog = { bark: <span><span>()<\/span> =&gt;<\/span> <span>void<\/span> };\r\n<span>type<\/span> Cat = { meow: <span><span>()<\/span> =&gt;<\/span> <span>void<\/span> };\r\n<span><span>function<\/span> <span>speak<\/span>(<span>animal: Dog | Cat<\/span>) <\/span>{\r\n  <span>if<\/span> (<span>\"bark\"<\/span> <span>in<\/span> animal) {\r\n    animal.bark();\r\n  } <span>else<\/span> {\r\n    animal.meow();\r\n  }\r\n}<\/code><\/pre>\n<p>\u89e3\u8aac<\/p>\n<p>\u3053\u306e\u4f8b\u3067\u306f Dog | Cat \u306e Union \u578b\u3092\u53d7\u3051\u53d6\u308a\u3001in \u6f14\u7b97\u5b50\u3092\u4f7f\u3063\u3066\u578b\u3092\u7d5e\u308a\u8fbc\u3093\u3067\u3044\u307e\u3059\u3002\u3053\u306e\u3088\u3046\u306a\u65b9\u6cd5\u3092 <strong>\u578b\u30ac\u30fc\u30c9\uff08Type Guard\uff09<\/strong> \u3068\u547c\u3073\u3001\u30ad\u30e3\u30b9\u30c8\u306a\u3057\u3067\u5b89\u5168\u306b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u578b\u3092\u5224\u5b9a\u3059\u308b\u624b\u6bb5\u3068\u3057\u3066\u5b9f\u52d9\u3067\u3082\u983b\u7528\u3055\u308c\u307e\u3059\u3002<\/p>\n<ul>\n<li>\n<p><strong>\u6291\u3048\u308b\u3079\u304d\u30dd\u30a4\u30f3\u30c8<\/strong>\uff1aUnion\u578b\u3092\u6271\u3046\u3068\u304d\u306f\u578b\u30ac\u30fc\u30c9\u3067\u5206\u5c90\u51e6\u7406\u3092\u660e\u78ba\u306b\u3059\u308b<\/p>\n<\/li>\n<li>\n<p><strong>\u6ce8\u610f\u70b9<\/strong>\uff1aas \u306b\u983c\u308a\u3059\u304e\u308b\u3068\u578b\u5b89\u5168\u304c\u640d\u306a\u308f\u308c\u308b\u306e\u3067\u3001\u307e\u305a\u306f\u30ac\u30fc\u30c9\u304b\u3089\uff01<\/p>\n<\/li>\n<\/ul>\n<hr>\n<h2>\u578b\u5909\u63db\u3092\u7406\u89e3\u3059\u308b\u3053\u3068\u306f\u300c\u578b\u3092\u5236\u3059\u308b\u300d\u7b2c\u4e00\u6b69<\/h2>\n<h3>\u672c\u8a18\u4e8b\u306e\u307e\u3068\u3081<\/h3>\n<ul>\n<li>\n<p>JavaScript\u306f\u300c\u6697\u9ed9\u5909\u63db\u300d\u306b\u6ce8\u610f\u3002\u660e\u793a\u7684\u5909\u63db\u3092\u7fd2\u6163\u5316\u3059\u308b<\/p>\n<\/li>\n<li>\n<p>Java\u3067\u306f\u300c\u30ad\u30e3\u30b9\u30c8\uff0b\u4f8b\u5916\u300d\u306b\u6ce8\u610f\u3002instanceof \u3092\u6d3b\u7528<\/p>\n<\/li>\n<li>\n<p>TypeScript\u306f\u300c\u578b\u30a2\u30b5\u30fc\u30b7\u30e7\u30f3\uff0b\u30ac\u30fc\u30c9\u300d\u3067\u5b89\u5168\u6027\u3092\u62c5\u4fdd<\/p>\n<\/li>\n<li>\n<p>\u5b9f\u52d9\u3067\u306f\u3001\u30d5\u30a9\u30fc\u30e0\u5165\u529b\u3001API\u30ec\u30b9\u30dd\u30f3\u30b9\u3001\u578b\u306e\u7570\u306a\u308b\u5909\u6570\u64cd\u4f5c\u306a\u3069\u3001\u578b\u5909\u63db\u306f\u65e5\u5e38\u8336\u98ef\u4e8b<\/p>\n<\/li>\n<li>\n<p>\u578b\u5909\u63db\u3092\u6b63\u3057\u304f\u4f7f\u3044\u3053\u306a\u3059\u3053\u3068\u304c\u3001\u30d0\u30b0\u9632\u6b62\u30fb\u54c1\u8cea\u5411\u4e0a\u306b\u3064\u306a\u304c\u308b<\/p>\n<\/li>\n<\/ul>\n<h3>\u3010\u5916\u90e8\u30ea\u30f3\u30af\u3011<\/h3>\n<p><a href=\"https:\/\/developer.mozilla.org\/ja\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Boolean\">MDN: Boolean()<\/a><\/p>\n<p><a href=\"https:\/\/developer.mozilla.org\/ja\/docs\/Web\/JavaScript\/Reference\/Global_Objects\/Number\">MDN: Number()<\/a><\/p>\n<p><a href=\"https:\/\/www.typescriptlang.org\/docs\/handbook\/2\/everyday-types.html\">TypeScript Handbook \u2013 Everyday Types<\/a><\/p>\n<p><a href=\"https:\/\/docs.oracle.com\/javase\/jp\/8\/docs\/api\/java\/lang\/Integer.html\">Java SE 8 API &#8211; java.lang.Integer<\/a><\/p>\n<h3>\u3010\u5185\u90e8\u30ea\u30f3\u30af\u3011<\/h3>\n<p><a href=\"https:\/\/route-zero.com\/recruit\/route\/1212\/\">\u975e\u540c\u671f\u51e6\u7406\u306e\u57fa\u672c\u3092\u7406\u89e3\uff5csetTimeout\u30fbPromise\u30fbasync\/await\u306e\u9055\u3044\u3068\u4f7f\u3044\u65b9<\/a><\/p>\n<p><a href=\"https:\/\/route-zero.com\/recruit\/route\/1205\/\">JavaScript\u3067CORS\u30a8\u30e9\u30fc\u304c\u51fa\u305f\u3068\u304d\u306e\u539f\u56e0\u3068\u5bfe\u51e6\u6cd5\u3092\u5fb9\u5e95\u89e3\u8aac<\/a><\/p>\n<p><a href=\"https:\/\/route-zero.com\/recruit\/route\/917\/\">JavaScript\u306e\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u304c\u308f\u304b\u3089\u306a\u3044\uff1f\u30a2\u30cb\u30e1\u30fc\u30b7\u30e7\u30f3\u5b9f\u4f8b\u3067\u3084\u3055\u3057\u304f\u89e3\u8aac\uff01<\/a><\/p>\n<\/div>\n","protected":false},"featured_media":1225,"template":"","_links":{"self":[{"href":"https:\/\/route-zero.com\/recruit\/wp-json\/wp\/v2\/route\/1219"}],"collection":[{"href":"https:\/\/route-zero.com\/recruit\/wp-json\/wp\/v2\/route"}],"about":[{"href":"https:\/\/route-zero.com\/recruit\/wp-json\/wp\/v2\/types\/route"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/route-zero.com\/recruit\/wp-json\/wp\/v2\/media\/1225"}],"wp:attachment":[{"href":"https:\/\/route-zero.com\/recruit\/wp-json\/wp\/v2\/media?parent=1219"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}