JavaScript: handy hint for jQuery document ready handlers

Like 99% of all jQuery users, I write the code I want executed when the document is ready like this:

$(function () {
  // code using $ for the jQuery function

Except… What happens if someone calls $.noConflict() and $ is no longer valid? Do I have to resort to using jQuery() all over the place, just to be sure?

Answer: no. It seems – and I only discovered this moments ago – the document ready handler gets passed the jQuery function as the first and only argument. You can write this instead:

jQuery(function ($) {
  // code using $ for the jQuery function

Or, if you are really paranoid:

jQuery(function ($, undefined) {
  // code using $ as the jQuery function
  // and undefined means what it says


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3 Responses

#1 Jason Bunting said...
02-Aug-11 10:23 AM

Well, an even better practice, that's been around for a long time now, is to do the following:

(function($) {

  /* any and all code for which you want to use the $ alias */

julian m bucknall avatar
#2 julian m bucknall said...
02-Aug-11 12:42 PM

Jason: Well sure (and I talked about this some months back), but it's no longer a document ready function. It's an autoexecuting anonymous function, or an Immediately-Invoked Function Expression (or IIFE).

They are different things, each with their place and utility.

Cheers, Julian

#3 Darron Driver said...
02-Aug-11 11:39 PM

A pattern I've found quite handy is:

var Setup = (function($) {
       // condition to be met
       if ($('#element_on_page')) {
    function _init() {
        // code to be executed
    return {

Has the advantage of being self-executing while still waiting for document ready. There is probably a better way of doing this, your thoughts?

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