{"provider_url":"https://hatena.blog","categories":["JavaScript"],"blog_url":"https://amachang.hatenablog.com/","html":"<iframe src=\"https://hatenablog-parts.com/embed?url=https%3A%2F%2Famachang.hatenablog.com%2Fentry%2F20070115%2F1168859275\" title=\" \u3053\u3093\u306a\u306b JavaScript \u3084\u3063\u3066\u308b\u306e\u306b\u77e5\u3089\u306a\u304b\u3063\u305f\u57fa\u672c\u6587\u6cd5\u300cif in\u300d - IT\u6226\u8a18\" class=\"embed-card embed-blogcard\" scrolling=\"no\" frameborder=\"0\" style=\"display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;\"></iframe>","description":"if \u301c in \u306a\u3093\u3066\u3042\u3063\u305f\u306e\u306d\u3002\u3002\u3002 \u77e5\u3089\u306a\u304b\u3063\u305f\uff01 \u4f7f\u3044\u5206\u3051 \uff13\u756a\u3081\u304c if in \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304c\u771f\u304b\u507d\u304b if (obj.property) { // ... } \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u3042\u308b\u304b\u306f\u7f6e\u3044\u3068\u3044\u3066 undefined \u3067\u306f\u306a\u3044\u3053\u3068\u3092\u78ba\u304b\u3081\u308b if (typeof obj.property == 'undefined') { // ... } \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306b\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u3042\u308b\u304b\u3002 if ('property' in obj) { // ... } \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u81ea\u4f53\uff08\u30d7\u30ed\u30c8\u30bf\u30a4\u30d7\u3092\u542b\u307e\u306a\u3044\uff09\u306b\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u3042\u308b\u304b if (obj.hasOwnProperty('property'))\u2026","author_url":"https://blog.hatena.ne.jp/amachang/","published":"2007-01-15 20:07:55","width":"100%","url":"https://amachang.hatenablog.com/entry/20070115/1168859275","title":" \u3053\u3093\u306a\u306b JavaScript \u3084\u3063\u3066\u308b\u306e\u306b\u77e5\u3089\u306a\u304b\u3063\u305f\u57fa\u672c\u6587\u6cd5\u300cif in\u300d","author_name":"amachang","height":"190","blog_title":"IT\u6226\u8a18","provider_name":"Hatena Blog","version":"1.0","image_url":null,"type":"rich"}