Iterating through an array

7.0 for-of: Traversing complex data types 7.0.1 es5--for-in traversing arrays

Used primarily to traverse JSON objects

let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let i in arr){    console.log(arr[i]);}//注释：for（创建一个变量）；in（in要遍历的复杂数据类型）

7.0.2 es6--for-of

遍历数组：let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let item of arr){    console.log(arr[item]);}//注释：for（创建一个变量）；of（of要遍历的复杂数据类型）遍历集合：let s = new Set [‘a‘,‘b‘,‘c‘,‘d‘];for(let item of s){    console.log(arr[item]);}遍历字符串：let str = ‘hello world‘;for(let item of str){    console.log(arr[item]);}遍历映射：let m = new Map[[‘a‘,‘b‘],[‘c‘,‘d‘]];for(let item of m){    console.log(arr[item]);}let m = new Map[[‘a‘,‘b‘],[‘c‘,‘d‘]];for(let [key,value] of m){    console.log(key,value);}

7.0.3 Extension: The Walker generation function (used with for-of). Keys (): Traversal key. VALUES (): Iterates over values, not for arrays. Entries (): Traversing Keys and values

let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let item of arr.keys()){    console.log(item);}let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let item of arr.values()){    console.log(item);}let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let item of arr.entries()){    console.log(item);}let arr = [‘a‘,‘b‘,‘c‘,‘d‘];for(let [k,v] of arr.entries()){    console.log(k,v);}

Iterating through an array