es6 Map与Set

es6 Map与Set

 

一:map

1.map的基本使用

    // map 基本使用
    let map = new Map();
    map.set('name','WHQ');
    map.set('age',24);
    map.set('未婚',true);
    console.log(map.get('name'));
    console.log(map.get('age'));
    console.log(map.get('未婚'));

2.key不是字符串类型

    // key是对象
    let obj = {};
    map.set(obj,'对象');
    console.log(map.get(obj));
    //
    // key是函数
    let func =function (){};
    map.set(func,'函数');
    console.log(map.get(func))

    // key 是NaN
    map.set(NaN,'NaN')
    console.log(map.get(NaN))
    console.log(map.get(Number('aaa')))

3.map的迭代

    // map迭代
    // for .. of
    for (let [key,value] of map) {
        console.log(key,value)
    }

    // foreach
    map.forEach(function(value, key, map){
        console.log(value,key,map.get(key))
    })

    // 所有的key
    for (let key of map.keys()){
        console.log(key)
    }

    // 所有的值
    for (let value of map.values()) {
        console.log(value)
    }

4.map的一些操作

 // Map对象操作
    // Map与Array转换

    // 数组转map
    let arr = [['k1','v1'],['k2','v2']]
    let map2 = new Map(arr)
    console.log(map2)

    // map转数组
    let arr2=Array.from(map2)
    console.log(arr2)

    // map合并 ...三点符号可以直接取值
    let map3=new Map([...map,...map2])
    console.log(map3)

二:set对象

1.set对象与map的区别

    // set里面的value值是唯一的
    // map允许有相同的value值
    let myMap = new Map();
    myMap.set('no001','张三');
    myMap.set('no002','李四');
    myMap.set('no003','张三');
    console.log(myMap)

    // set里面的value值是唯一的
    let mySet=new Set();
    mySet.add('张三')
    mySet.add('李四')
    mySet.add('张三')
    console.log(mySet)

2.set遍历

    // set遍历
    // for ... of
    for (let value  of mySet.values()) {
        console.log(value)
    }

    // forEach遍历
    mySet.forEach(function (value) {
        console.log(value)
    })

3.set 转数组

    //Set 转数组
    let arr3 =[['k1','v1'],[['k2','v2']]];
    let set3 = new Set(arr3)
    console.log(set3)

    //直接三点运算符,转数组
    let arr4 = [...set3]
    console.log(arr4)

4.数组去重操作

    // 数组去重
    let arr5 = [1,3,5,3,6];
    let set6=new Set(arr5)
    let arr6=[...set6]
    console.log(arr6)

    // 求并集
    let a = new Set([1, 2, 3]);
    let b = new Set([4, 3, 2]);
    let union = new Set([...a,...b]);// {1, 2, 3, 4}
    console.log('求并集')
    console.log(union)

    // 求交集
    let a2 = new Set([1, 2, 3]);
    let b2 = new Set([4, 3, 2]);
    let intersect = new Set([...a].filter(x =>b2.has(x)));// {2, 3}
    console.log('求交集')
    console.log(intersect)

    //求差集
    let a3 = new Set([1, 2, 3]);
    let b3 = new Set([4, 3, 2]);
    let differenceA3 = new Set([...a3].filter(x => !b3.has(x)));// {1}
    let differenceB3 = new Set([...b3].filter(x => !a3.has(x))); //{4}
    console.log('求差集')
    console.log(differenceA3)
    console.log(differenceB3)