New features in jQuery 3.0

We received a big present for the 10th anniversary of jQuery, jQuery 3.0 has reached beta status. Let’s take a look at what’s new in jQuery and how to use it.

jQuery.Deferred Updated to be Promises/A+ Compatible

Quoting https://promisesaplus.com/

A promise represents the eventual result of an asynchronous operation. The primary way of interacting with a promise is through its then method, which registers callbacks to receive either a promise’s eventual value or the reason why the promise cannot be fulfilled.

The promises in jQuery was a problem before (more you can read on stackoveflow). At least they are fixed.

New .data() implementation

The new implementation is closer to HTML5 dataset specification. All keys are now converted from kebab-case to camelCase, regardless of access method. One important notice: digits no longer take part in this conversion.
For example: foo-bar and fooBar will be same, but foo-23 and foo23 not. More on below image from jsbin.com:

Deprecated methods .load(), .unload() and .error() are removed

They were deprecated since jQuery 1.8. To handle above events correctly we should use on method. For example:

$( "#element" ).on( "load", function() {
    // implementation
});

I’m pretty sure that a library with above extensions will be released soon :)

##.unwrap now with selector The selector allows to be specific about which wrappers should we remove. Before it was impossible.

Speed-up for some jQuery custom selectors

Paul Irish at Google make a huge detective work and identified some cases where a bunch of extra work can be skipped for custom selectors. For example selector :visible is 17 times faster now.

This change actually was made in 1.12/2.2, but was reiterated for jQuery 3.0.

Better handling of error cases

Incorrect requests which have been ignored till now. Simple example: $("#") now throws an error rather than returning empty collection.

Animations

Because all modern browsers support requestAnimationFrame (more on caniuse.com), jQuery will use this API when performing animations. Main advantage is smoother animations and less CPU-intensive animations.