this.method = function（）{} VS obj.prototype.method = function（）{} [英] this.method = function(){} VS obj.prototype.method = function (){}

问题描述

作为一名c＃/ .net开发者，我喜欢在业余时间用JavaScript来玩弄 - 创建我自己的库/框架等等。无可否认，它们并不多（实际上只不过是一组松散的函数），但目的是学习;不适合其他人使用。

我通常以这种方式扩展一个基本的JavaScript对象

 < code $ obj = function（）{
 //基本对象的东西
 this.method = function（）{
 //其他的东西
}; 
返回此; 
}; 
  

这允许我一起创建其他对象和链式方法，这实际上是光滑的：

  obj（'arg1'）。method（）; 
  

两个例子： jQuery Knock-off ，列表-Item Sorter

然而，我最近看到，在比我自己更多的函数代码中，对象通过这种方式实现了相同的功能：

$ $ p $ function obj（）{
// stuff
}
obj.prototype.method = function（） {
// stuff
};


示例： Reddit Chrome扩展

两种方式似乎都达到了相同的目的，我对这两种语法的看法都不是部分的。有没有一种比另一种更有用的特殊情况？
$ b

编辑

这些方法提供了什么使他们比其他人更受欢迎？请看下面的代码：

  var dice = function（sides）{
 this.roll（）{
 return 4 //保证是随机的
} 
}; 
 
 var d1 =骰子（6）; 
 d1.roll（）// 4; 
 var d2 =骰子（20）; 
 d2.roll（）// 4 
  

d1和d2是不同的对象，因为它们在我看来？或者它们是指向一个对象（var dice）的指针/昵称？

解决方案

  this。 method = function（）{}; 
  

仅适用于特定实例。

  Obj.prototype.method = function（）{}; 
  

将适用于 Obj

尽管为了利用原型，您应该这样做

  var o = new Obj（）; //请注意，旨在与新一起使用的函数应该大写
 
 o.method（）; 
  

---

骰子示例

我假设您打算在 dice（）函数中返回这个。

该示例并不常见，因为调用函数不会创建新对象。在你的骰子的情况下，你将为这个分配一个方法，该函数内部是 window 全局对象，然后返回它。

在中结果将是相同的对象（ window ）。 d1 和 d2 ，方法 roll 将在第二次调用中重新分配。

要达到你想要的效果，你应该使用 new 来创建实例，如下所示：

  var d1 = new Dice（6）; //记住大写在这里很重要
 var d2 = new Dice（20）; 
  

这会创建2 roll 函数，这是正确的，但浪费内存，因为该功能可以通过做共享：

  Dice.prototype.roll = function（）{/ *返回随机awesomeness * /}; 
  

希望澄清事情

As a c#/.net dev, I love to toy around with JavaScript in my spare time -- creating my own libraries/frameworks and such. Admittedly, they're not much (really nothing more than a loose collections of functions), but the purpose is to learn; not for other people to use.

I usually extend a basic JavaScript object this way

obj = function () {
    //basic object stuff
    this.method = function () {
        //other stuff
    };
    return this;
};

This allows me to create other objects and chain methods together, which is really slick:

obj('arg1').method();

Two Examples: jQuery Knock-off, List-Item Sorter

However, I have recently seen, in much more function code than my own, objects accomplish the same functionality this way:

function obj(){
    //stuff
}
obj.prototype.method = function () {
    //stuff
};

Example: Reddit Chrome Extension

Both ways seem to accomplish the same end, and I'm not partial to the look of either syntax. Is there a particular situation where one would be more useful than the other? What do these methods offer that makes them more desirable than the other?

Edit

Consider the following code:

var dice = function (sides) {
    this.roll(){
        return 4 //guaranteed to be random
    }
};

var d1 = dice(6);
d1.roll()  // 4;
var d2 = dice(20);
d2.roll()  // 4

Are d1 and d2 different objects, as they appear to me? Or are they pointers/nicknames to one object (var dice)?

解决方案

this.method = function(){};

Only works for that specific instance.

Obj.prototype.method = function(){};

Will work for every instance of Obj

Though in order to take advantage of prototype you should do

var o = new Obj(); // Note that functions intended to be used with "new" should be capitalized

o.method();

---

Dice Example

I'll assume you intended to return this in your dice() function.

That example is not really common, because calling a function does not create a new object. In your dice case you would be assigning a method to this, which inside the function is window the global object, and then returning it.

The outcome would be the same object (window) in both d1 and d2, with a method roll which would be reassigned in the 2nd call.

To achieve what you want you should create the instances with new, like this:

var d1 = new Dice(6); // remember capitalization is important here
var d2 = new Dice(20); 

This will however create 2 roll functions, which is correct but wastes memory since the function can be shared by doing:

Dice.prototype.roll = function() { /* return random awesomeness */ };

Hope that clarifies things

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