When to use this in javascript OO?

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? E.g 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

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 2

You should use 'this'.

Answer 3

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

Answer 4

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 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

I have found 3 Ways to define a javascript class helpful.

Answer 7

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: http://stackoverflow.com/questions/1007340/javascript-function-aliasing-doesnt-seem-to-work/1162192#1162192