let se = new Set([1,2,3]);
console.log(se);
//Set(3) {1, 2, 3}
let ws = new WeakSet([{name: "张三"}]);
console.log(ws);
//WeakSet {Object {name: "张三"}}成员必须是对象
let me = new Map([["name","张三"]]);
console.log(me);
//Map(1) {"name" => "张三"}
const wm = new WeakMap([[{}, 'foo']]);
console.log(wm);
//WeakMap {Object {} => "foo"}成员的属性名必须是对象
