Weird JavaScript statement, what does it mean?

Question

I see this code, what's it doing?

var obj = this;

What part of that are you confused about? [this](http://www.quirksmode.org/js/this.html)? — Blorgbeard, Mar 28 '11 at 15:39
we will need to know in which context (within which function was this?).. — amosrivera, Mar 28 '11 at 15:39
Answer: It’s a [variable statement](http://bclary.com/2004/11/07/#a-12.2) with a variable declaration that initializes the declared variable *obj* with the value of *this*. — Gumbo, Mar 28 '11 at 15:50

score 5 · Answer 1 · answered Mar 28 '11 at 15:41

5

It's just storing the current reference of this object, to be used in future. It's useful, because in JS value of this depends on a context.

answered Mar 28 '11 at 15:41

wildcard

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score 3 · Answer 2 · answered Mar 28 '11 at 15:40

3

It saves a reference to whatever this was in the current context, so it can be used later.

answered Mar 28 '11 at 15:40

gen_Eric

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2

Where "later" propably means "in closures". – Mar 28 '11 at 16:02

Town · Answer 3 · 2011-03-28T15:45:49.800

1

It's creating a variable 'obj' and setting it to the current context.

So, for example, if it's at a global level this would be the current DOM Window.

edited Mar 28 '11 at 15:45

answered Mar 28 '11 at 15:39

Town

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score 1 · Answer 4 · answered Mar 28 '11 at 15:40

That is setting a local copy of the current first class function that its being set in.

This is used ALOT in jquery as this takes on a different meaning when you being using the selectors.

Say I have a

function Person() {
   this.name = "gnostus";
}

and I need to access name from inside a jquery selector, where this becomes an html element, I would store my object into a copy variable and use, obj.name in place of this.name when im inside of the jquery context.

I do somehow suspect that jQuery is the context of this question. — Kzqai, Jun 19 '11 at 23:57

score 1 · Answer 5 · answered Mar 28 '11 at 15:43

It depends where this statement is located. It assigns to variable "obj" reference to current object.

for example the following code will open an alert window and show [Window object]. That's because we check value of "this" in the body area (not inside any objects event handler, etc.)

<html>
    <head>
    </head>
    <body>

    <script type="text/javascript">

        alert(this);
    </script>   

    </body>
</html>

score 0 · Answer 6 · answered Mar 28 '11 at 15:40

0

var obj = this;

Is stating, assign obj with the parent of the current scope.

I first read this post a couple months ago to get a handle on the keyword 'this'.

http://justin.harmonize.fm/index.php/2009/09/an-introduction-to-javascripts-this/

answered Mar 28 '11 at 15:40

Mike Lewis

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score 0 · Answer 7 · answered Mar 28 '11 at 15:40

0

The this keyword is used to refer to the owner of the function , or the variable the this keyword is used in. For a detailed understanding visit http://www.quirksmode.org/js/this.html

answered Mar 28 '11 at 15:40

Neeraj

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score 0 · Answer 8 · answered Mar 28 '11 at 15:43

The only context I can think of where this sort of code makes sense is to make the current context (this) available inside a closure.

So the code would be something like:

var obj = this;
setTimeout(function() {
    obj.someMethod();
}, 1000);

That would call the method "someMethod" on the current context object after 1 second goes by.

Weird JavaScript statement, what does it mean?

8 Answers8

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