如何有效地计算JavaScript中对象的键/属性数量？

问题：

What's the fastest way to count the number of keys/properties of an object? 计算对象的键/属性数的最快方法是什么？ It it possible to do this without iterating over the object? 是否可以在不迭代对象的情况下执行此操作？ ie without doing 即不做

var count = 0;
for (k in myobj) if (myobj.hasOwnProperty(k)) count++;

(Firefox did provide a magic __count__ property, but this was removed somewhere around version 4.) （Firefox确实提供了一个神奇的__count__属性，但此属性已在版本4的某个位置删除。）

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解决方案：

参考一： https://stackoom.com/question/Wns/如何有效地计算JavaScript中对象的键-属性数量
参考二： https://oldbug.net/q/Wns/How-to-efficiently-count-the-number-of-keys-properties-of-an-object-in-JavaScript

来源：oschina

链接：https://my.oschina.net/u/4438370/blog/4479622