<script>// 數組已經幫我們內置這個Iterator接口let arr = ['hello','world'];let map = arr[Symbol.iterator](); // 數組直接調用iterator接口，返回一個對象mapconsole.log(map.next()); // {value: "hello", done: false} done:循環沒有下一步狀態：true沒有，false:有狀態，循環并沒有結束console.log(map.next()); // {value: "world", done: false}console.log(map.next()); // {value: undefined, done: true}</script>

<script>let obj ={  start: [1,5,7],  end:[8,4,3],  [Symbol.iterator](){   let self = this;   let index = 0;   let arr = self.start.concat(self.end);   let len = arr.length;   return {    next(){     if(index<len){      return{       value:arr[index++],       done:false      }     }else{      return {       value:arr[index++],       done:true      }     }    }   }  }}for(let key of obj){ // for...of 背后用的就是iterator接口  console.log(key); // 1 5 7 8 4 3}</script>

<script>let arr = ['xixiaoxian','jamin'];for(let value of arr){  console.log(value); // xixiaoxian  jamin}</script>