jQuery 1.5 Released

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Right on schedule jQuery 1.5 is ready for consumption!

This release has been a long time coming and has been a real team effort. Please take this opportunity to thank members of the jQuery Team and the jQuery bug triage team for their help in getting this release out the door.


As usual, we provide two copies of jQuery, one minified and one uncompressed (for debugging or reading).

You can feel free to include the above URLs directly into your site and you will get the full performance benefits of a quickly-loading jQuery.

Additionally you can also load the URLs directly from Microsoft and Google’s CDNs:

Microsoft CDN: http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.5.min.js

Google CDN: https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js

About The Release

This release saw 83 fixed bugs and a total of 460 closed tickets.

The test suite (which now has 4437 tests) passes in all the browsers that jQuery supports – and more. We verified the suite passing all of the following browsers:

  • Safari 5.0.3 / 4.0.5 / 3.2.3 / 3.1.2
  • Opera 11.01 / 11 / 10.63 / 10.54 / 10.10 / 9.64
  • IE 6 / 7 / 8
  • Firefox 4.0b9 / 3.6.13 / 3.5.11 / 3.0.19 /
  • Chrome 8.0.552.215 / 8.0.552.237 / 9.0.597.67 Beta / 10.0.642.2 Dev

Additionally all of the API documentation for the release can be found on the API site: jQuery 1.5 API Documentation.

A full schedule of our upcoming releases can be found on our roadmap. Right now we’re planning on doing major jQuery releases more frequently (likely a couple times a year, rather than once per year).

So, without further ado, what’s changed in jQuery 1.5?

Ajax Rewrite

Easily the largest change in this release is the complete rewrite of the Ajax module in jQuery. This rewrite helps to fix a lot of gaps that existed in the old Ajax system along with providing a higher level of consistency across the API.

Perhaps the largest change is that a call to jQuery.ajax (or jQuery.get, jQuery.post, etc.) now returns a jqXHR object that provides consistency to the XMLHttpRequest object across platforms (and allows you to perform previously-impossible tasks like aborting JSONP requests).

More details concerning the new jqXHR object can be found in the jQuery.ajax() documentation.

In addition to a more consistent API the Ajax system is now much more extensible – allowing you to attach all sort of data handlers, filters, and transports. These changes should open up a whole realm of new Ajax plugins that can take advantage of this extensibility. More information can be found in the Extending Ajax documentation. The team is actively soliciting feedback on the Ajax extensibility API and if you have any feedback please feel free to direct it to the Developing jQuery Forum.

Deferred Objects

Along with the rewrite of the Ajax module a new feature was introduced which was also made publicly available: Deferred Objects. This API allows you to work with return values that may not be immediately present (such as the return result from an asynchronous Ajax request). Additionally it gives you the ability to attach multiple event handlers (something that wasn’t previously possible in the Ajax API).

For example, the following is now possible with jQuery’s internal Ajax API:

// Assign handlers immediately after making the request,
// and remember the jqxhr object for this request
var jqxhr = $.ajax({ url: "example.php" })
    .success(function() { alert("success"); })
    .error(function() { alert("error"); })
    .complete(function() { alert("complete"); });

// perform other work here ...

// Set another completion function for the request above
jqxhr.complete(function(){ alert("second complete"); });

Additionally you can make your own deferred objects using the exposed jQuery.Deferred. More information about this API can be found in the Deferred Object documentation.

Eric Hynds has written up a good tutorial on Using Deferreds in jQuery 1.5.


jQuery now exposes a new way in which you can create and modify a clone of jQuery – all while still taking advantage of the full jQuery API. For example, you could use it to override native jQuery methods without actually affecting the methods that other users would interact with – or even create encapsulated APIs for your plugins that avoid namespace collision.

Here is a sample of adding a method to a jQuery sub so that it isn’t exposed externally:

    var sub$ = jQuery.sub();

    sub$.fn.myCustomMethod = function(){
      return 'just for me';

    sub$(document).ready(function() {
      sub$('body').myCustomMethod() // 'just for me'

  typeof jQuery('body').myCustomMethod // undefined

More information about jQuery.sub() can be found in the API documentation.

Note that if you’re looking to use this for plugin development, you should first strongly consider using something like the jQuery UI widget factory which manages both state and plugin sub-methods. Some examples of using the jQuery UI widget factory to build a plugin.

Adjacent Traversal Performance

In this release we’ve also been able to improve the performance of some commonly-used traversal methods: .children(), .prev(), and .next(). The speed-ups that we’re seeing are quite substantial (potentially many many times faster, depending upon the browser).

.children() Performance in jQuery 1.5

.prev() Performance in jQuery 1.5

.next() Performance in jQuery 1.5

Performance Test Case and Raw Numbers

Build System

Finally, we’ve made some changes to jQuery’s internal build system. We’ve worked to standardize all of our build process upon the excellent server-side JavaScript environment: NodeJS. We especially appreciate this as we’re able to reduce our dependency upon legacy Java/Rhino systems and focus more squarely on up-and-coming JavaScript environments.

Additionally with this switch we’ve moved to using UglifyJS from the Google Closure Compiler. We’ve seen some solid file size improvements while using it so we’re quite pleased with the switch.


As always we want to thank everyone that helped with this release – without your contributions this release would not have been possible. If you have any questions or spot any bugs please submit your issues to the jQuery bug tracker.

170 thoughts on “jQuery 1.5 Released

  1. Felicito Sinceramente de todo corazón al equipo de JQuery, es un excelente trabajo, les deseo todo lo mejor y aqui estamos aprendien mas de Jquery

  2. Dear author of this post i like the jQuery as well as me. but are you really sure about look of jQuery home page


    the boook block you show not look better in chrome firefox and IE. i not know which one browser you use to test the look.

    see the section book about jQuery on home page. the mockup have something missing.

    well solve that.

  3. Azsenz on said:

    Just tested and it breaks the jQuery Tools Date/Calendar overlay which was working previously in 1.4.4. Looks like jQuery Tools will have to make an update but there hasn’t been much activity out of them for a while.

  4. It would be interesting to hear the back story about that huge speed increase for .children() in Chrome. In JQuery 1.4 Chrome is rather low, in 1.5 the increase is ridiculous. Tapping into some native functionality, I suppose.

  5. Great news!
    Way to go, jQuery team.

    Rock solid and very backwards compatible!
    You care about javascript developers using your library.
    Explains you’re number 1.

  6. Just impressed with the performance improvement. But, why Chrome & Safari show remarkable improvements, while others lag?
    Is there any special reason?

  7. In this sentence “which you can create and modify and clone of jQuery” from the jQuery.sub() section, it should be “a clone” instead, right?

  8. Saul Montalvo Perales on said:

    Excellent work, Jhon!!! Thank you all guys!!! Congratulations for all the team.

    Regards from Monterrey, Mexico