javascript一種新的物件建立方式-Object.create()

yupeng發表於2013-12-17
JavaScript物件Object

1.Object.create() 是什麼？

　　Object.create(proto [, propertiesObject ]) 是E5中提出的一種新的物件建立方式，第一個引數是要繼承的原型，如果不是一個子函式，可以傳一個null，第二個引數是物件的屬性描述符，這個引數是可選的。

　　例如：　

function Car (desc) {
    this.desc = desc;
    this.color = "red";
}
 
Car.prototype = {
    getInfo: function() {
      return 'A ' + this.color + ' ' + this.desc + '.';
    }
};
//instantiate object using the constructor function
var car =  Object.create(Car.prototype);
car.color = "blue";
alert(car.getInfo());

結果為:A blue undefined.

2.propertiesObject 引數的詳細解釋：（預設都為false）

　資料屬性

  • writable:是否可任意寫
  • configurable：是否能夠刪除，是否能夠被修改
  • enumerable：是否能用 for in 列舉
  • value：值

　訪問屬性：

  • get(): 訪問
  • set(): 設定

3.例子：直接看例子就知道怎麼用。　

<!DOCTYPE html>
<html>
<head>
    <title>yupeng's document </title>
    <meta charset="utf-8"/>
</head>
<body>
    <script type="text/javascript">

        var obj = {

            a:function(){
                console.log(100)
            },
            b:function(){
                console.log(200)
            },
            c:function(){
                console.log(300)
            }

        }

        var newObj = {};

        newObj = Object.create(obj,{
            t1:{
                value:'yupeng',
                writable:true
            },
            bar: {
                configurable: false,
                get: function() { return bar; },
                set: function(value) { bar=value }
            }
            
        })

        console.log(newObj.a());
        console.log(newObj.t1);
        newObj.t1='yupeng1'
        console.log(newObj.t1);
        newObj.bar=201;
        console.log(newObj.bar)
        
        function Parent() { }
        var parent = new Parent();
        var child = Object.create(parent, {
              dataDescriptor: {
                value: "This property uses this string as its value.",
                writable: true,
                enumerable: true
              },
              accessorDescriptor: {
                get: function () { return "I am returning: " + accessorDescriptor; },
                set: function (val) { accessorDescriptor = val; },
                configurable: true
              }
            });

        child.accessorDescriptor = 'YUPENG';
        console.log(child.accessorDescriptor);



        var Car2 = function(){
            this.name = 'aaaaaa'
        } //this is an empty object, like {}
        Car2.prototype = {
          getInfo: function() {
            return 'A ' + this.color + ' ' + this.desc + '.';
          }
        };

        var newCar = new Car2();
         
        var car2 = Object.create(newCar, {
          //value properties
          color:   { writable: true,  configurable:true, value: 'red' },
          //concrete desc value
          rawDesc: { writable: true, configurable:true, value: 'Porsche boxter' },
          // data properties (assigned using getters and setters)
          desc: { 
            configurable:true, 
            get: function ()      { return this.rawDesc.toUpperCase();  },
            set: function (value) { this.rawDesc = value.toLowerCase(); }  
          }
        }); 
        car2.color = 'blue';
        console.log(car2.getInfo());
        car2.desc = "XXXXXXXX";
        console.log(car2.getInfo());
        console.log(car2.name);



    </script>
</body>
</html>

結果為：

100
yupeng
yupeng1
201
I am returning: YUPENG
A blue PORSCHE BOXTER.
A blue XXXXXXXX.
aaaaaa
 
參考文章：
1.http://www.htmlgoodies.com/beyond/javascript/object.create-the-new-way-to-create-objects-in-javascript.html
2.http://www.jimmycuadra.com/posts/ecmascript-5-object-creation-and-property-definition
3.http://msdn.microsoft.com/zh-cn/library/ie/ff925952(v=vs.94).aspx

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