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 |