【JavaScript】Map和Set

JavaScript中Map和Set

ES6新特性

Map和Set

Map

• 定义

var mp = new Map([["tom",100],["jack",90],["nick",80]]);

• 通过key获得value

var mp = new Map([["tom",100],["jack",90],["nick",80]]);
var values = mp.get("tom");//通过key获得value

• 新增或修改值

    var mp = new Map([["tom",100],["jack",90],["nick",80]]);
    var values = mp.get("tom");//通过key获得value

    mp.set("admin",99); //新增或修改值

• 根据key删除值

    var mp = new Map([["tom",100],["jack",90],["nick",80]]);
    var values = mp.get("tom");//通过key获得value

    mp.set("admin",99); //新增或修改值
    mp.delete("tom");   //根据key删除值

Set 无序不重复的集合

• set特性

var st = new Set([3,1,2,1]);

• 添加元素

    var st = new Set([3,1,2,1]);
    st.add(9);

• 删除元素

    var st = new Set([3,1,2,1]);
    st.add(9);
    st.delete(3);

• 是否包含

    var st = new Set([3,1,2,1]);
    st.add(9);
    st.delete(3);
    console.log(st.has(9));

iterator迭代器，for…of

• 遍历数组

    var arr = [3,4,5];
    for(let i of arr){
    
    
        console.log(i);
    }

• 遍历Map

    var mp = new Map([["tom",100],["jack",90],["nick",80]]);

    for(var x of mp){
    
    
        console.log(x);
    }

• 遍历Set

    var st = new Set([3,1,2,1]);
    
    for(let s of st){
    
    
        console.log(s);
    }