迭代器 -》实现原理

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        // 遍历器-》迭代器   // iterator 实现原理
        // class Iterator{
        //     constructor(arr){
        //         this.arr = arr;
        //         this.index = 0;
        //     }
        //     next(){
        //         let index = this.index,
        //             arr = this.arr;

        //         if(index > arr.length - 1){
        //             return {
        //                 done: true,
        //                 value: undefined
        //             }
        //         } 

        //         return {
        //             done: false,
        //             value: arr[this.index++] 
        //         }
              
        //     };
        // }

        // let arr = [10,20,30];
        // let itor = new Iterator(arr);
        // console.log(itor.next());  // {done: false, value: 10}
        // console.log(itor.next());  // {done: false, value: 20}
        // console.log(itor.next());  // {done: false, value: 30}
        // console.log(itor.next());  // {done: true, value: undefined}

       
        // let arr = [10,20,30];
        // arr[Symbol.iterator] = function(){
        //     let index = 0,
        //         self = this; 
        //     return {
        //         next(){
        //             if(index > self.length -1){
        //                 return {
        //                     done:true,
        //                     value:undefined
        //                 }
        //             }
        //             return {
        //                 done:false,
        //                 value:self[index++]
        //             }
        //         }
        //     }
        // }
        // for(let item of arr){
        //     console.log(item);
        // }


        /**
         *  对象类数组使用for of 遍历
        */

        // let obj = {
        //     0:10,
        //     1:20,
        //     2:30,
        //     3:40,
        //     length:4,
        //     [Symbol.iterator]:Array.prototype[Symbol.iterator]
        //     // [Symbol.iterator]:function(){
        //     //     let index = 0,
        //     //         self = this; 
        //     //     return {
        //     //         next(){
        //     //             return index > self.length -1 ? {
        //     //                 done:true,
        //     //                 value:undefined
        //     //             } : {
        //     //                 done:false,
        //     //                 value: self[index++]
        //     //             }
        //     //         }
        //     //     };
        //     // }
        // }

        // for(let item of obj){
        //     console.log(item);
        // }


        // Object.prototype.sex = '男';
        // Object.prototype[Symbol.iterator] = function(){
        //     let self = this,
        //             index = 0,
        //             keys = [
        //                 ...Object.getOwnPropertyNames(self),
        //                 ...Object.getOwnPropertySymbols(self)
        //             ];  
        //         return {
        //             next(){
        //                return index > keys.length - 1 ? {
        //                     done:true,
        //                     value:undefined
        //                } : {
        //                     done:false,
        //                     value:self[keys[index++]]
        //                }
        //             }
        //         }     
        // }

        // // 遍历对象
        // let obj = {
        //     name:'Eric',
        //     age:11,
        //     [Symbol('AA')]:100 
        // }

        // for(let item of obj){
        //     console.log(item);
        // }

        // console.log(obj);

 

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posted @ 2021-07-28 16:55  13522679763-任国强  阅读(20)  评论(0)    收藏  举报