how does jquery make the $ do what it does?

Question

In order to use the $ symbol in jquery and not have to use jQuery.functionname, we use this

(function($) {

})(jQuery);

(In drupal, you actually have to specify this implicitly).

I don't understand this javascript syntax, why is there an initial parentheses? How is the (jQuery) at the end used?

It's an *immediately invoked anonymous function expression.* Has been discussed untold times before. `$` is simply a variable name. — deceze, Oct 30 '13 at 16:46
the first function variable is $ and then you're calling it passing jQuery....and what he said ^ — rorypicko, Oct 30 '13 at 16:47
I'm sure I was discussed elsewhere, but I didn't know how to look it up. I looked up immediate invoked javascript and now I found the answer. Thanks. — user1015214, Oct 30 '13 at 16:49
Understand closure [here](http://stackoverflow.com/questions/111102/how-do-javascript-closures-work) — Murali Murugesan, Oct 30 '13 at 16:50
@deceze It's not necessarily easy to find that information if you don't know what the construct is called (and why would you if you don't know what it is), though. — Anthony Grist, Oct 30 '13 at 16:51
Self executing ananymous function which passes `jQuery` as parameter — Murali Murugesan, Oct 30 '13 at 16:51
@Anthony Admittedly, yes, absolutely. But some random googling and poking around should have let to that conclusion sooner or later IMO. — deceze, Oct 30 '13 at 18:56

score 1 · Answer 1 · answered Oct 30 '13 at 16:47

It's just an anonymous function with an argument that's automatically invoked.

For example, if we were to expand it out a bit you'd end up with something like this:

var anon = function($) {
    ...
};

anon(jQuery);

The $ is a valid identifer in JavaScript and we pass in the existing jQuery object into the function for use through $, as it could be replaced later.

score 0 · Answer 2 · edited May 23 '17 at 10:32

All that's doing is declaring an anonymous function and executing it immediately, passing in one argument (jQuery) into the function. That argument is given the name $ which can be used throughout the scope of the function.

The brackets around the function aren't strictly necessary in all contexts; see the comment under this answer for details. The gist is that they're needed here to make the function behave like an expression instead of a statement (function declaration).

how does jquery make the $ do what it does?

2 Answers2