1     let arr = [1,2,3];
 2 
 3     for (let i of arr) {
 4       console.log(i);
 5       
 6     }
 7 
 8     let obj = {
 9       name: ‘obj1‘
10     }
11 
12     console.log(arr);    //array拥有了iterator接口
13     console.log(...arr); //三点运算符用的也是iterator接口
14     console.log(obj);
15 
16     for (let i of obj) {
17       console.log(i);     //object对象没有iterator接口
18       
19     }

 1     //模拟实现iterator接口
 2     function iteratorUtil(target) {
 3       let index = 0;    //用来表示指针其实位置
 4       return {          //返回指针对象
 5         next() {        //指针对象的next方法
 6           return index < target.length ? {
 7             value: target[index++],
 8             done: false
 9           } : {
10             value: target[index++],
11             done: true
12           };
13         }
14       }
15     }
16 
17     //生成一个迭代器对象
18     let arr = [1,2,3];
19     let iteratorObj = iteratorUtil(arr);
20     console.log(iteratorObj.next().value);
21     console.log(iteratorObj.next().value);
22     console.log(iteratorObj.next().value);
23     console.log(iteratorObj.next().value);

 1 let arr = [1,2,3,4];
 2 
 3     var obj = {name: ‘kobe‘, age: 40};
 4     //    console.log(obj[Symbol.iterator]); // undefined
 5     //    console.log(arr[Symbol.iterator]); // function
 6 
 7     function mockIterator() {
 8 
 9       let that = this;
10 
11       let index = 0;
12       let length = 0;
13       debugger
14       if(that instanceof Array){
15         length = that.length;
16         return {
17           next: function () {
18             return index < length ?{value: that[index++], done: false}: {value: that[index++], done: true}
19           }
20         }
21       }else {
22         length = Object.keys(that).length
23         let keys = Object.keys(that);
24         return {
25           next: function () {
26             return index < length ?{value: that[keys[index++]], done: false}: {value: that[keys[index++]], done: true}
27           }
28         }
29       }
30 
31     }
32 
33   
34 
35     Array.prototype[Symbol.iterator] = mockIterator;
36     Object.prototype[Symbol.iterator] = mockIterator;
37 
38     for(let i of arr){
39       console.log(i);
40     }
41     for(let i of obj){
42       console.log(i);
43     }