Question

I’m using JQuery UI to addClass(), and later to removeClass().

If removeClass() is called before addClass() completes, it queues up and executes later. This is not ideal, I’d rather have the removeClass() execute immediately from the current CSS values.

If I invoke stop() just before add/removeClass(), animation seems permanently ‘frozen’ at the moment of the stop() call, though the add/removeClass() callback still fires.

Just the JS here:

var obj = $("#obj");
obj.addClass("obj");

$("#add").click(function(){
    //obj.addClass("adder", 2000, "easeInOutCubic", onAdded);
    obj.stop().addClass("adder", 2000, "easeInOutCubic", onAdded);
});

$("#remove").click(function(){
    //obj.removeClass("adder", 2000, "easeInOutCubic", onRemoved);
    obj.stop().removeClass("adder", 2000, "easeInOutCubic", onRemoved);
});

function onAdded () { console.log("added"); }
function onRemoved () { console.log("removed"); }

All the rest here: http://jsfiddle.net/mmstM/42/

This seems like it would be a common issue but haven’t found any good info on SO or elsewhere…note this is for JQuery UI, not core.

Answer 1

The issue is occurring because even after the class is removed, the interstitial size rules generated for the animation are still present in the element’s style property.

We can fix that part trivially by doing:

obj.stop().attr("style", "").removeClass("adder", 2000, "easeInOutCubic", onRemoved);

However, this causes a rather sizeable jump in the animation for the reason that easings for class manipulation don’t take element styles into account – the same reason why simply clearing the queue in the first place didn’t work. The quick solution to this, I fear, is pretty ugly: using the .animate() method instead, and moving the styles from the class to your jQuery, like so:

$("#add").click(function(){
    //obj.addClass("adder", 2000, "easeInOutCubic", onAdded);
    obj.stop().animate({
        width: '200px',
        height: '80px',
    }, 2000, "easeInOutCubic", onAdded);
});

$("#remove").click(function(){
    //obj.removeClass("adder", 2000, "easeInOutCubic", onRemoved);
    obj.stop().animate({
        width: '40px',
        height: '40px',
    }, 2000, "easeInOutCubic", onRemoved);
});

You can check out the working example here, with a bonus hack to load the width/height values from CSS and stash them in objects to mimic the add/removeClass() syntax.