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Showing content from https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Set/has below:

Set.prototype.has() - JavaScript | MDN

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Set 实例的 has() 方法返回一个布尔值来指示对应的值是否存在于该集合中。

const set1 = new Set([1, 2, 3, 4, 5]);

console.log(set1.has(1));
// Expected output: true

console.log(set1.has(5));
// Expected output: true

console.log(set1.has(6));
// Expected output: false

value

要测试是否存在于 Set 对象中的值。

如果 Set 对象中存在具有指定值的元素，则返回 true；否则返回 false。

const mySet = new Set();
mySet.add("foo");

console.log(mySet.has("foo")); // true
console.log(mySet.has("bar")); // false

const set1 = new Set();
const obj1 = { key1: 1 };
set1.add(obj1);

console.log(set1.has(obj1)); // true
console.log(set1.has({ key1: 1 })); // false, 因为它们是不同的对象引用
console.log(set1.add({ key1: 1 })); // 现在 set1 包含 2 个条目

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