第188天：extend拷贝创建对象的原理

一、拷贝创建对象的原理

  //拷贝创建对象核心代码
     function extend(target,source) {
         //遍历对象
         for(var i in source){
             target[i] = source[i];
         }
         return target;
     }

     //游戏随机生成名字
        var boy = {
         name:'无忌'
         ,image:'男性头像'
         ,age:20
         ,sex:'男'
     };

     var gril = {
         name:'风晴雪'
         ,age:18
         ,image:'女性头像'
         ,sex:'女'
     };

     var zuixiake = extend({}, boy);
     zuixiake.name='醉侠客';
     console.log(zuixiake.name);//醉侠客
     console.log(zuixiake.sex);//男

二、拷贝进阶用法

 <script>

     //extend2实现的功能：extend(target,obj1,obj2,obj3)

    function extend () {
         var key,i = 0,len = arguments.length,target = null,copy;
         if(len === 0){
             return;
         }else if(len === 1){
             target = this;
         }else{
             i++;
             target = arguments[0];
         }
         for(; i < len; i++){
             for(key in arguments[i]){
                 copy = arguments[i][key];
                 target[key] = copy;
             }
         }
         return target;
     }

     function extend2(){
         for (var p in source) {
             if (source.hasOwnProperty(p)) {
                 target[p] = source[p];
             }
         }

         return target;
     }

     //游戏随机生成名字
     var boy = {
         name:'无忌'
         ,image:'男性头像'
         ,age:20
         ,sex:'男'
     };

     //技能名称，等级，伤害值，需要的魔法
     var technology = {tname:'亡灵复活',tlevel:10,tstrength:3000,tmagic:30};

     var shenqi = {sname:'霜之哀伤',slevel:30,sstrength:3000};
     //当这个人有了穿上盔甲，圣衣，六神合体，戴上魔法戒指之后，自动也拥有一个技能

     //第一种用法
     var zuixiake = extend({}, technology,shenqi);
     zuixiake.name='醉侠客';
     console.log(zuixiake.name);//醉侠客
     console.log(zuixiake.tname);//亡灵复活
     console.log(zuixiake.sname);//霜之哀伤

     //第二种用法
    extend(boy,technology,shenqi);
     console.log(boy.name);//无忌
     console.log(boy.tname);//亡灵复活
     console.log(boy.sname);//霜之哀伤

 </script>