ES6之map

map为键值对集合

   let m = new Map();
        m.set('name', '小白');
        m.set('chang', function() {
            console.log("改变自己");
        })

        let key = {
            school: 'NONGDA'
        };
        m.set(key, ['beijing', 'shanghai', 'shenzhen']);

        console.log(m);
        //size
        console.log(m.size);
        //删除
        m.delete('name');

        //获取
        console.log(m.get('chang'));
        console.log(m.get(key));
        //晴空
        m.clear();
        //遍历

        for (let v of m) {
            console.log(v);

        }

map其实就是一个升级版的对象