如何查看大 JSON 对象是否包含值？

我正在使用 PHP 对大量多维事件数组进行 json 编码，所以我得到如下内容：

var ents = {"7":{"event_id":"7","nn":"The Whisky Drifters","nn_url":"the-whisky-drifters",
  "venue":"The Grain Barge","date_num":"2010-06-11","date_txt":"Friday 11th June",
  "gig_club":"1","sd":"A New Acoustic String Band...","ven_id":"44",
  "art":0},"15":{"event_id":"15","nn":"Bass Kitchen","nn_url":"bass-kitchen",
  "venue":"Timbuk2","date_num":"2010-06-11","date_txt":"Friday 11th June",
  "gig_club":"2","sd":"Hexadecimal \/ DJ Derek \/ Id","ven_id":"21",
  "art":1},

第一个维度是 id，请参见

var ents = {"7":{

因此可以在不检查嵌套对象的情况下获取 id...

检查 JSON 是否包含 id 的最快、最有效的方法是什么？

您可以使用hasOwnProperty https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Object/hasOwnProperty method:

if (ents.hasOwnProperty('7')) {
  //..
}

此方法检查对象是否包含指定的属性，无论其值如何。

比in https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Operators/Special_Operators/in_Operator运算符，因为它不检查继承的属性。