使用對(duì)象模擬模擬實(shí)現(xiàn)pop/push，shift/unshift

"use strict"

 let users = {
    0:{name: "Zhao", age: 23},
    1:{name: "Qian", age: 21},
    2:{name: "Sun", age: 25},

   length: 3,

    //在末端刪除一個(gè)對(duì)象并返回
    pop(){

      //容錯(cuò)機(jī)制：length為 0 時(shí) users 對(duì)象為空
      if(this.length == 0){
        alert("刪除失敗，users 為空")
        return;
      }

      //臨時(shí)保存要?jiǎng)h除的屬性
      let moment = this[this.length - 1];
      
      //刪除屬性
      delete this[this.length - 1];
      
      //length 自減
      this.length--;

      return moment;
    },
    
    //在末端添加一個(gè)對(duì)象
    push(user){
      this[this.length] = {name:user.name,age:user.age};
      this.length++;
    },

    //在首端刪除一個(gè)對(duì)象,并返回被刪除對(duì)象
    shift(){
      //提取要?jiǎng)h除對(duì)象
      let userName = this[0].name;
      let userAge = this[0].age;

      //元素左移一位
      if(this.leftMove()){
      
      //this.length自減
      this.length--;

      return {userName, userAge};
      }
      else{
        alert("操作失??！");
        return;
      }
    },

    //在首端添加一個(gè)對(duì)象
    unshift(user){
      //右移
      this.rightMove();

      //首端添加對(duì)象
      this[0] = user;

      //this.length自增
      this.length++;

      return;
    },

    //



    //將 users 整體元素左移一位
    //this.length == 0 返回 false，否則返回 true
    leftMove(){
      //length == 0 返回false
      if(this.length == 0){
        return false;
      }
      for(let i = 0; i < this.length - 1; i++){
        this[i] = object.assign({}, this[i + 1]);
      }
      return true;

 },

    //將 users 整體元素右移一位
    rightMove(){
      if(this.length == 0){
        return;
      }
      for(let i = this.length - 1; i >= 0; i--){
        //復(fù)制 this[i] 的副本并返回給 this[i + 1]
        this[i + 1] = Object.assign({}, this[i]);
      }
    }
}

//-------------------------------------------------------分割線-------------------------------------------------------
 //測(cè)試用例
 function printUsersFn(){
    alert("指令集: \n1.pop \n2.push \n3.unshif\n" +
            "4.shift \n520.printEvery");
 }
 //指令輸入
 function scanfOlder(){
    return prompt("請(qǐng)輸入指令", "");
 }
 //屬性輸入,并返回一個(gè)對(duì)象
 function scanfItem(){
    let name = prompt("請(qǐng)輸入名稱(chēng)：","");
    let age = prompt("請(qǐng)輸入年齡：","");

    return {name,age};
 }
 //打印所有對(duì)象
 function printEvery(users){
    let userStr = "";
    for(let i = 0; i < users.length; i++){
      userStr += `${users[+i].name} + ${users[+i].age} \n`;
    }
    alert(userStr);
 }

 //指令枚舉
 function userFn(users){
   switch(scanfOlder()){
    case '1':users.pop();                 break;    //尾端刪除一個(gè)元素
    case '2':users.push(scanfItem());     break;    //尾端添加一個(gè)元素
    case '3':users.unshift(scanfItem());  break;    //首端添加一個(gè)元素
    case '4':users.shift();               break;    //首端刪除一個(gè)元素
    case 'length':alert(users.length);    break;    //打印 users.length
    case '520':printEvery(users);         break;    //打印所有元素
    default:alert("指令錯(cuò)誤！");
   }
 }

 while(true){
   //打印指令集
   printUsersFn();

   //輸入指令并執(zhí)行
   userFn(users);

 }