在Javascript中附加到原型或对象实例的方法有什么区别？ [英] What is difference between method attached to prototype or object instance in Javascript?

问题描述

我对Javascript中原型的使用有点困惑。

让我们看下面的例子：

（1）

 
 function Rectangle（w，h）{
 this.width = w; 
 this.height = h; 
 this.area = function（）{this.width * this.height; } 
} 
 

以及类似的情况，其中区域附加到原型如下：

（2）

 
函数Rectangle（w，h）{
 this.width = w ; 
 this.height = h; 
} 
 Rectangle.prototype.area = function（）{this.width * this.height; } 
 

• （1）和（2）之间的差异是什么？


• 何时使用（1）或（2）来写类方法？

解决方案

 函数矩形（w，h）{
 var rect = { }; 
 rect.width = w; $ b $ c rect.height = h; 
 rect.area = function（）{return this.width * this.height; }; 
 return rect; 
} 
  

vs

  var Rectangle = {
 area：function（）{return this.width * this.height; } 
} 
 
 function rectangle（w，h）{
 var rect = Object.create（Rectangle）; 
 rect.width = w; 
 rect.height = h; 
 return rect; 
} 
  

这个想法很简单，你把常用的东西放在一个原型对象上，然后你继承它。

至于何时想使用原型？总是。

当然，你可能想要用糖改善ES5 OO

I am a bit confused about the usage of prototypes in Javascript.

Let's take the following example:

(1)

   function Rectangle(w, h) { 
      this.width=w; 
      this.height=h; 
      this.area=function() { this.width * this.height; }
   }

And a similar case where the area is attached to a prototype as follows:

(2)

   function Rectangle(w, h) { 
      this.width=w; 
      this.height=h; 
   }
   Rectangle.prototype.area=function() { this.width * this.height; }

• What is the diffrence between (1) and (2) ?
• When would you use (1) or (2) for writing methods on classes?

解决方案

prototypes are best shown differently.

function rectangle(w, h) {
    var rect = {};
    rect.width=w; 
    rect.height=h; 
    rect.area=function() { return this.width * this.height; };
    return rect;
}

vs

var Rectangle = {
    area: function() { return this.width * this.height; }
}

function rectangle(w, h) {
    var rect = Object.create(Rectangle);
    rect.width=w; 
    rect.height=h; 
    return rect;
}

The idea is simple, you put common stuff on a prototype object and you then inherit from it.

As for when you want to use the prototype? Always.

Of course you probably want to Improve ES5 OO with sugar

这篇关于在Javascript中附加到原型或对象实例的方法有什么区别？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！