es6知識點for..of vs for...in

es6知識點for..of vs for...in

預設具有遍歷器介面的數據結構,for of迴圈 當對一個數據結構使用for of迴圈遍歷的時候，會自動調用遍歷器介面。 ES6中有四類數據結構預設具有遍歷器介面: （1）數組 （2）某些類數組 （3）Map （4）Set

for of 遍歷

var arr = [1,2,3,4,5,6];
    //不同迴圈遍歷
    for(let i = 0;i<arr.length;i++){
        console.log(arr[i]);
    }
    arr.forEach(i=>{
        console.log(i);
    });

    //用迭代器遍歷
    let iterator = arr[Symbol.iterator]();
    let result =iterator.next();
    while(!result.done){
        console.log(result.value);
        resulf = iterator.next();
    }
    
    //for of 遍歷
    //array
    for(let item of arr){
        console.log(item);
    }
    //set
    let s = new Set(["a","b","c"]);
    for(let item of s){
        console.log(item);
    }
    //map
    let m = new Map([["name","薑薑"],["age",23]]);
    for(let item of m){
        console.log(item);
    }

for in

let obj = {x:1,y:2,z:3};
let arr = ["a","b","c"];
for(let key in obj){
    console.log(key);
    console.log(obj[key]);
}
for(let key in arr){
    console.log(key);
    console.log(arr[key]);
}