javascript一种新的对象创建方式-Object.create()

时间:2021-11-17 13:00:00

1.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.

2.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

3.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
参考文章:
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