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该新特性属于 ECMAScript 2015（ES6）规范，在使用时请注意浏览器兼容性。
Size属性将会返回Set对象中元素的个数。
说明
Size的值表示Set对象拥有多少个元素。通过调用函数的形式访问Size会提示为undefined；并且该值不能够被更改。
例子
使用
var mySet = new Set();
mySet.add(1);
mySet.add(5);
mySet.add("some text")
mySet.size; // 3
规范
| Specification | Status | Comment |
|---|---|---|
| Standard | 初始定义 | |
| Draft |
浏览器兼容
We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | 38 | 19 (19) [1] | 11 | 25 | 7.1 |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | 未实现 | 38 | 19.0 (19) | 未实现 | 未实现 | 8 |
[1] From Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10) to Gecko 18 (Firefox 18 / Thunderbird 18 / SeaMonkey 2.15 / Firefox OS 1.0.1 / Firefox OS 1.1) the size property was implemented as a Set.prototype.size() method, this has been changed to a property in later versions conform to the ECMAScript 6 specification (bug 807001).