map、weakmap

知识点一：map

1、作用：存储键值对 

let map = new Map([[key,value],[key2,value2]])

map.set(key,value)
map.get(key)
map.delete(key)
map.has(key)
map.clear()
// map中key可以是任意的属性，比如数字、字符串、对象、bool...

2、常用的API

• set
• get
• delete
• has
• clear

map.set(3, '数字');
    console.log(map);

    let obj = { name: 'zs' };
    map.set(obj, '对象类型');
    console.log(map);

    let symbol = Symbol('symbol');
    map.set(symbol, 'symbol类型');
    console.log(map);

    map.set(true, 'bool');
    console.log(map);

    console.log(map.size);

    console.log(map.has(3));

    map.delete(3);
    console.log(map);

　　map.clear();
　　consoole.log(map);

3、遍历map：forEach()遍历

let map = new Map([['键1','值1'],['键2', '值2'],['键3', '值3'],['键4', '值4']]);
        console.log(map.entries());
        console.log(map.keys());
        console.log(map.values());

        map.forEach((values, keys) => {
            console.log(values);
        })

 

知识点二：weakmap

1、WeakMap的键只能是引用类型

2、使用new WeakMap()创建

3、常用API

• set
• get
• delete
• has
• clear

let weakMap = new WeakMap([[{ name: 'zs' }, "值1"], [{ age: 18 }, "值2"]]);
    console.log(weakMap);