ui.widget: don't trigger 'remove' event for non-widget elements

[amakhrov]

An updated version of the previous pull request

ui.widget overrides the $.cleanData method to also call .triggerHandler( "remove" ) method. According to Chrome's profiler, triggerHandler is a relatively slow method.

When element is being removed with $(elem).remove(), $.cleanData is called for each descendant element - and there can be thousands of those elements!

This is an attempt to only execute triggerHandler( "remove" ) for elements that are jQueryUI Widgets and skip that for all other elements.

Benchmark - pure jQuery vs jQueryUI vs fixed jQueryUI

[scottgonzalez]

@rwaldron Can we get a ruling on storing a boolean directly on a DOMElement?

[scottgonzalez]

If I'm reading that benchmark right, you used a single element for the entirety of the body? This is a horrible representation of what happens in real pages.

[amakhrov]

You're right.
But why do you think it's relevant in the context of this issue?

When an element (on a real page) is removed, jquery gets all its descendant elements (with getElementsByTagName("*")) and then passes this list to .cleanData.
The performance issue I came across is related to the fact the slow piece of code inside .cleanData is called for every single element of this list.

This is the updated benchmark - http://jsperf.com/jquery-ui-remove-elements/2
Here the removed element has 1000 child nodes, which is closer to real life and to what I have in my app.

Does it make sense to you?

[scottgonzalez]

But why do you think it's relevant in the context of this issue?

Because your first benchmark shows that this takes less than 1ms in the browsers you tested. That's not a bottleneck.

The performance issue I came across is related to the fact the slow piece of code inside .cleanData is called for every single element of this list.

Is your new benchmark showing the actual problem you're facing? The benchmark shows that this is running in about 13ms for 1000 elements being removed. That's about the speed of setTimeout(function() {}, 0) in many browsers.

[amakhrov]

Ok, I see you point now.

In my app I render a list of 2000+ items, each of which has some markup inside, so total nodes are 16000+
the benchmark with 16000 elements is here: http://jsperf.com/jquery-ui-remove-elements/2
with the original jquery ui it takes me significant time to remove it.

[scottgonzalez]

This was fixed by #1291.