{"height":"190","author_name":"takuya_1st","width":"100%","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Ftakuya-1st.hatenablog.jp%2Fentry%2F2015%2F11%2F28%2F035522\" title=\" Array(10) \u304cundefined \u306b\u306a\u308b\u554f\u984c\u3002 - \u305d\u308c\u30de\u30b0\u3067\uff01\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","image_url":null,"provider_url":"https://hatena.blog","version":"1.0","provider_name":"Hatena Blog","author_url":"https://blog.hatena.ne.jp/takuya_1st/","title":" Array(10) \u304cundefined \u306b\u306a\u308b\u554f\u984c\u3002","url":"https://takuya-1st.hatenablog.jp/entry/2015/11/28/035522","type":"rich","categories":["javascript"],"published":"2015-11-28 03:55:22","description":"js \u3067\u8981\u7d20\u304c\u7a7a\u3063\u307d\u306e\u914d\u5217\uff11\uff10\u500b\u4f5c\u3063\u3066\u30eb\u30fc\u30d7\u5909\u6570\u4ee3\u308f\u308a\u306b\u4f7f\u3063\u3066\u307f\u3088\u3046 for\u30eb\u30fc\u30d7\u3068\u304b\u30c0\u30eb\u3044\u3088\u306d\u3068\u601d\u3063\u3066\u3002\uff11\uff10\u500b\u30eb\u30fc\u30d7\u5909\u6570\u3057\u3066\u307f\u305f\u3089\u3002\u3002\u3002 Array(10).forEach( (e)=>{ console.log(e) } ) //=> undefined \u3042\u308c\uff1f\u306a\u3093\u3067\uff1f map \u3067\u521d\u671f\u5316\u3057\u305f\u3089\uff1f Array(10).map( (x)=>{return 1} ) [undefined \u00d7 10] \u3042\u308c\uff1f\u51fa\u6765\u306a\u3044\u3002 \u914d\u5217\u306e\u9577\u3055\u306f\uff11\uff10\u3060\u3088\u306d\uff1f \u3046\u3093\u3001\u914d\u5217\u9577\u306f\u6307\u5b9a\u901a\u308a\u306a\u3093\u3067\u3059\u306d\u3001 Array(10).length //=> 10 \u3042\u308c\uff1f undefined \u306e\u6271\u3044\u306e\u554f\u984c\u304b\u306a\uff1f Array(10)[\u2026","blog_title":"\u305d\u308c\u30de\u30b0\u3067\uff01","blog_url":"https://takuya-1st.hatenablog.jp/"}