{"id":4181,"date":"2025-07-13T12:00:56","date_gmt":"2025-07-13T03:00:56","guid":{"rendered":"https:\/\/dennie.tokyo\/it\/?p=4181"},"modified":"2025-12-07T19:12:16","modified_gmt":"2025-12-07T10:12:16","slug":"%e3%80%90javascript%e3%80%91undefined-%e3%81%a8-null","status":"publish","type":"post","link":"https:\/\/dennie.tokyo\/it\/?p=4181","title":{"rendered":"\u3010JavaScript\u3011undefined \u3068 NULL"},"content":{"rendered":"\n<p>JavaScript \u306b\u89e6\u308c\u3066\u3044\u308b\u3068 undefined \u3068\u3044\u3046\u3082\u306e\u3092\u898b\u308b\u6a5f\u4f1a\u304c\u3042\u308a\u307e\u3059\u3002<br>\u305d\u308c\u3068 null \u3068\u3044\u3046\u306e\u3082\u898b\u308b\u4e8b\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<!--more-->\n\n\n\n<p>\u306a\u3093\u3068\u306a\u304f\u3001\u3053\u308c\u3089\u306f\u540c\u3058\u3088\u3046\u306a\u3082\u306e\u3060\u308d\u3046\u3068\u601d\u3063\u3066\u3044\u307e\u3057\u305f\u304c\u53b3\u5bc6\u306b\u306f\u9055\u3046\u3088\u3046\u306a\u306e\u3067\u3001\u81ea\u5206\u306a\u308a\u306b\u307e\u3068\u3081\u3066\u307f\u307e\u3057\u305f\u3002<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">undefined \u3068\u306f<\/h1>\n\n\n\n<p>\u8a00\u8449\u3068\u3057\u3066\u306f\u300c\u672a\u5b9a\u7fa9\u300d\u3068\u3044\u3046\u610f\u5473\u306b\u306a\u308a\u307e\u3059\u3002JavaScript \u306e undefined \u3092\u898b\u3066\u307f\u308b\u3068\u6982\u306d\u3053\u306e\u89e3\u91c8\u3067\u5408\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">undefined \u304c\u300c\u672a\u5b9a\u7fa9\u300d\u3068\u3044\u3046\u4e8b<\/h1>\n\n\n\n<p>\u5b9f\u969b\u306b JavaScript \u3067 undefined \u304c\u767a\u751f\u3059\u308b\u4f8b\u3092\u898b\u306a\u304c\u3089 undefined \u304c\u300c\u672a\u5b9a\u7fa9\u300d\u3068\u3044\u3046\u4e8b\u3092\u898b\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u307e\u305a\u3001\u5909\u6570\u306f\u5024\u304c\u8a2d\u5b9a\u3055\u308c\u3066\u3044\u306a\u3051\u308c\u3070 undefined \u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-js\" data-lang=\"JavaScript\"><code>let val;\nconsole.log(val); 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