一种新的javascript对象创建方式Object.create()

时间:2020-05-14 yupeng 人气:0

Object.create() 是什么？
Object.create(proto [, propertiesObject ]) 是E5中提出的一种新的对象创建方式，第一个参数是要继承的原型，如果不是一个子函数，可以传一个null，第二个参数是对象的属性描述符，这个参数是可选的。
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());

结果为:A blue undefined.

1、propertiesObject 参数的详细解释：（默认都为false）
数据属性：

writable:是否可任意写
configurable：是否能够删除，是否能够被修改
enumerable：是否能用 for in 枚举
value：值

访问属性：

get(): 访问
set(): 设置

2、例子：直接看例子就知道怎么用。　

<!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>

结果为：
100
yupeng
yupeng1
201
I am returning: YUPENG
A blue PORSCHE BOXTER.
A blue XXXXXXXX.
aaaaaa

以上就是针对javascript一种新的对象创建方式Object.create()的详细介绍，希望对大家的学习有所帮助。

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