ES6-遍历方法 for of

• 遍历数组

let arr = [1,2,3,4,5];
for (let item of arr){
     console.log(item);
     //1
     //2
     //3
     //4
     //5
}

• 遍历字符串

let str = 'helloword';
for(let char of str){
     console.log(char);
}

• 遍历nodeList(标签节点)

let p = document.getElementByTagName('p');
for(let i of p){
     console.log(i);
}

• 遍历Set

let set1 = new Set([1,2,3,4,5]);
for (let s of set1){
     console.log(s);
}

• 遍历Map

let m = new Map([
    ['123','qwe'],
    ['234','wer'],
    ['345','ert'].
]);
for(let m1 of m){
    console.log(m1);
    //['123', 'qwe']  ['234', 'wer']  ['345', 'ert']
}
//循环Map中的key
var mk = m.keys();
for(let k of mk){
    console.log(k);//123 234 345
}
//循环Map中的value
var mv = m.values();
for(let v of mv){
    console.log(v);//qwe  wer  ert
}

• 循环对象

var obj = {
    names:'qwe',
    age:123,
    sex:"男",
}
//对象没有iterator，所以不能用 for of 循环
for(let key in obj){
    console.log(obj[key]);//names  age  sex
    //打印所有键名
    console.log(obj[key]);//qwe  123  男
    //打印所有的value
}