CODEWITHSUNDEEP
javascript
Suresh kumar
Suresh kumar

Reputation: 505

What does "this" mean in this revealing module pattern

var abc=(function(){

     var self=this;

     return {
        self:self
     }             


})();

When doing abc.self I get undefined what does this happen to be in this context.

Upvotes: 4

Views: 74

Answers (3)

Denys Séguret
Denys Séguret

Reputation: 382344

What you have can be simplified for the purpose of the explanation in

(function(){ console.log(this) })();

Your expression (in the first set of parenthesis) defines a function. You then call this function without context (the this). This construct is called an IIFE. As you don't pass a context, the behavior depends whether it is called in strict mode or not :

  • In non strict mode, you would have the global object (window in a browser, global in node).

  • In strict mode, a missing context of a function call isn't replaced, it's undefined.

As you get undefined, I guess you're in strict mode. You probably have "use strict"; at the start of the file or in an enclosing function.

If you wanted to pass a context, you might for example have done

(function(){ console.log(this) }).call(someobject);

Upvotes: 4

Bhojendra Rauniyar
Bhojendra Rauniyar

Reputation: 85573

this refers to the current object. In your condition this will be window, and as you're trying to get the value abc.self, you need to use like this:

this.self = this;

Now, only you can get the value:

var xyz = new abc();
xyz.self

But to note, you cannot use abc as the constructor like above code because you are using the closure.

Upvotes: 1

john Smith
john Smith

Reputation: 17926

in that "root scope" this is window

and 

console.log(abc.self);

results for me in 

Window {top: Window, window: Window, ...}

Upvotes: 1

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