What is the significance of this function definition?
javascript, jquery
Solution
An immediately invoked function expression which aliases `jQuery` to `$` inside its scope:
(function($) {}(jQuery));
It creates and executes a function immediately. This way you can use `$` inside the function to reference jQuery regardless of what the global `$` references to. Useful for pages using `jQuery.noConflict()`. Also the variables declared inside that IIFE don't leak to the global scope.
As for the other part of the question, `$.fn === jQuery.prototype`. So by adding a method to the jQuery prototype, you may call it on any jQuery object. E.g.:
$.fn.doSomething = function(){}; //add a method to the jQuery prototype
$('selector').doSomething(); //then you may call it on any jQuery object
More on jQuery plugin authoring.
Problem
I understand how to define functions like this: ``` function myfunc(x,y,z) { alert("Just an example " + x + y + z) } ``` But not this: ``` <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script> <script> (function ($) { $.fn.idle = function (x, y, z) { alert("Just an example " + x + y + z) }(jQuery)); </script> ``` The above is a part of a library I'm using, but I simply can't understand the `$.fn.idle` bit. What is it doing? It's defining a function called 'idle', somehow, but what about the `$.fn`? And what about the `(function ($) {` part? Again, I understand `$(document).ready(function() {` but `(function ($) {` is completely alien. Is it a short hand? And what is the significance of the `(jQuery));` at the bottom?