Set.prototype.size
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Set 实例的 size 访问器属性将返回该集合中（唯一的）元素的个数。
尝试一下
const set1 = new Set();
const object1 = {};
set1.add(42);
set1.add("forty two");
set1.add("forty two");
set1.add(object1);
console.log(set1.size);
// Expected output: 3
描述
size 的值是一个整数，表示 Set 对象有多少条目。size 的 set 访问函数是 undefined；你无法改变这个属性。
示例
使用 size
js
const mySet = new Set();
mySet.add(1);
mySet.add(5);
mySet.add("some text");
console.log(mySet.size); // 3
规范
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-get-set.prototype.size |