WeakSet.prototype.has()

const weakset1 = new WeakSet();
const object1 = {};
const object2 = {};

weakset1.add(object1);

console.log(weakset1.has(object1));
// Expected output: true

console.log(weakset1.has(object2));
// Expected output: false

has(value)

const ws = new WeakSet();
const obj = {};
ws.add(window);

ws.has(window); // 返回 true
ws.has(obj); // 返回 false

// 存储非全局注册的符号
const sym = Symbol("foo");
ws.add(sym);
ws.add(Symbol.iterator);