什么时候在javascript OO中使用它？

Question

In Javascript OO, when should I use the this keyword?

Also, if I want to call a method of a class from another method of the same class, should I use this or just the name of the function? Eg is this correct?

function Foo()
{
   this.bar= function()
   {
      alert('bar');
   }

   this.baz= function()
   {
     this.bar(); //should I use this.bar() or just bar()?
   }
}

Answer 1

When it comes to "object-oriented" JavaScript, here's a nice guide Mark Dickinson here on SO linked to: Private Members in JavaScript . It does go into detail about some other stuff you don't really need now, but once you understand how JavaScript works, you'll see that it's quite different from your ordinary object-oriented language when it comes to things like what this really means.

I'd say that in your case, you should definitely use this , but maybe your functions should be in the prototype part of your "class" (this avoids redefining the function every time a new instance is created.)

Answer 2

我找到了3种方法来定义一个有用的javascript类 。

Answer 3

In this particular instance, it's best to use a self-referencing variable in the place of this to prevent confusion and headaches inside functions.

function Foo()
{
   var self = this;

   this.bar= function()
   {
      alert('bar');
   }

   this.baz= function()
   {
     self.bar();
   }
}

The reason for it is because since everything in javascript is an object, the this keyword inside a function refers to the parent function. By defining a variable at a certain scope, your guaranteed that variable will maintain its scope.

Answer 4

Just to stress and empathize previous answer of @tj111 I suggest you to read this . To better understand function scoping.

Answer 5

The correct version is the one that doesn't give an error when you try to call the function. If you omit this you will get a ReferenceError exception.

Answer 6

In another post about 'function aliasing' in JavaScript, I explained in detail, with examples, how 'this' works in JavaScript. I think it may be useful to you.

Please check: JavaScript function aliasing doesn't seem to work