These are the different types of Document Ready functions typically used in jQuery (aka jQuery DOM Ready). A lot of developers seem to use them without really knowing why. So I will try to explain why you might choose one version over another. Think of the document ready function as a self-executing function which fires after the page elements have loaded.
See Where to Declare Your jQuery Functions for more information on how to use the Document Ready Functions.
Document Ready Example 1
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| $(document).ready(function() { //do jQuery stuff when DOM is ready}); |
Document Ready Example 2
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| $(function(){ //jQuery code here }); |
This is equivalent to example 1… they literally mean the same thing.
Document Ready Example 3
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| jQuery(document).ready(function($) { //do jQuery stuff when DOM is ready}); |
Adding the jQuery can help prevent conflicts with other JS frameworks.
Why do conflicts happen?
Conflicts typically happen because many JavaScript Libraries/Frameworks use the same shortcut
name which is the dollar symbol $. Then if they have the same named functions the browser gets
confused!
Conflicts typically happen because many JavaScript Libraries/Frameworks use the same shortcut
name which is the dollar symbol $. Then if they have the same named functions the browser gets
confused!
How do we prevent conflicts?
Well, to prevent conflicts i recommend aliasing the jQuery namespace (ie by using example 3 above).
Then when you call $.noConflict() to avoid namespace difficulties (as the $ shortcut is no longer available)
we are forcing it to wrtie jQuery each time it is required.
Well, to prevent conflicts i recommend aliasing the jQuery namespace (ie by using example 3 above).
Then when you call $.noConflict() to avoid namespace difficulties (as the $ shortcut is no longer available)
we are forcing it to wrtie jQuery each time it is required.
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| jQuery.noConflict(); // Reverts '$' variable back to other JS librariesjQuery(document).ready( function(){ //do jQuery stuff when DOM is ready with no conflicts }); //or the self executing function way jQuery.noConflict(); (function($) { // code using $ as alias to jQuery})(jQuery); |
Document Ready Example 4
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| (function($) { // code using $ as alias to jQuery $(function() { // more code using $ as alias to jQuery });})(jQuery);// other code using $ as an alias to the other library |
This way you can embed a function inside a function that both use the $ as a jQuery alias.
Document Ready Example 5
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| $(window).load(function(){ //initialize after images are loaded }); |
Sometimes you want to manipulate pictures and with $(document).ready() you won’t be able to do that
if the visitor doesn’t have the image already loaded. In which case you need to initialize the
jQuery alignment function when the image finishes loading.
if the visitor doesn’t have the image already loaded. In which case you need to initialize the
jQuery alignment function when the image finishes loading.