jQuery 3.1.0 Released – No More Silent Errors

July 7th, 2016

Not so long ago, we released jQuery 3.0. One of the major features of jQuery 3.0 was a small rewrite of jQuery Deferreds. Specifically, we made them compatible with the Promises/A+ spec. That basically meant that errors had to be silenced and passed as rejection values to rejection handlers (added using deferred.catch()). This had the advantage of preventing Promise handlers from getting blocked up by runtime errors, but the disadvantage of errors being silenced if no rejection handlers were added. While this was the right move for Deferreds, we had also changed jQuery.ready and jQuery.fn.ready to use the new spec-compliant Deferreds under the covers.

Unfortunately, if you were using the usual ways to attach ready handlers (e.g. jQuery(function() {}) and jQuery(document).ready(function() {})), you had no way to add a rejection handler. Plus, it wasn’t obvious that you were in Deferred land. Any runtime exceptions were getting swallowed and lost in space. I think they ended up somewhere near Pluto, which isn’t even a planet anymore! There were workarounds, but this wasn’t acceptable to us.

We immediately set out to fix this, and thus jQuery 3.1.0 was born. No longer will errors be silent! You will see them logged to the console by default. If you’d like to have more control on how these errors are handled, we also added an entry point: jQuery.readyException. In most cases, you won’t need to use it, but any errors that are thrown within a ready handler will get passed to this function should you need it.

jQuery.readyException = function(error) {
  // "error" is thrown from any ready handler

The default jQuery.readyException will re-throw the error asynchronously, to avoid stopping execution and log the error to the console. We hope this solves any debugging issues you may have experienced when using jQuery 3.0.

We do not expect this release to have any breaking changes, but if you do encounter bugs in upgrading from the previous version, please let us know.

If you’d like help upgrading from jQuery 1.x or 2.x to jQuery 3.0, please check out the 3.0 Upgrade Guide and the jQuery Migrate 1.4.1 blog post.

3.1.0GitHub changelog


You can include these files directly from the jQuery CDN if you like, or copy them to your own local server.

Slim build

Sometimes you don’t need ajax, or you prefer to use one of the many standalone libraries that focus on ajax requests. And often it is simpler to use a combination of CSS and class manipulation for all your web animations. Along with the regular version of jQuery that includes the ajax and effects modules, we’ve released a “slim” version that excludes these modules. All in all, it excludes ajax, effects, and currently deprecated code. The size of jQuery is very rarely a load performance concern these days, but the slim build is about 6k gzipped bytes smaller than the regular version – 23.6k vs 30k. These files are also available in the npm package and on the CDN:

These updates are already available as the current versions on npm and Bower. Information on all the ways to get jQuery is available at Public CDNs receive their copies today, please give them a few days to post the files. If you’re anxious to get a quick start, use the files on our CDN until they have a chance to update.

Many thanks to all of you who participated in this release by testing, reporting bugs, or submitting patches, including Oleg Gaidarenko, Michał Gołębiowski, and the whole jQuery team.