switchClass() removes class if removeClass and addClass params are the same

[gtasker10]

I am using jQuery 3.6.0. Seems to be an undocumented "feature" with switchClass(). If I specify the same class to remove and then add, I get no class. In the following example, I would expect to see class="big":

   <input type="text" id="myInput" class="big"></input>
   <script>
      $(document).ready(function () {
         $("#myInput").switchClass("big", "big");
      });
   </script>

The above generates:

<input type="text" id="myInput" class="">

[mgol]

Thanks for the report. Does the issue you describe exist when jQuery UI 1.12.1 is used or only with jQuery UI 1.13.0 or newer?

[markvantilburg]

it's also in v1.12

https://jsfiddle.net/jgh7eu0w/

[markvantilburg]

https://github.com/jquery/jquery-ui/blob/9180a8180b17c38f6c3f27ba46d4546d800d3508/ui/effect.js#L232

do nothing

if(remove === add){return;}

or

		if(remove === add){
			return $.effects.animateClass.call( this, {
			add: add
		}, speed, easing, callback );
		} else {
		return $.effects.animateClass.call( this, {
			remove: remove,
			add: add
		}, speed, easing, callback );
		}

[mgol]

Thanks for the report. Since the issue is already in 1.12, given limited team resources it's not likely to be fixed by the UI team; see the project status at https://blog.jqueryui.com/2021/10/jquery-maintainers-update-and-transition-jquery-ui-as-part-of-overall-modernization-efforts/. PRs are welcome if they're not too complex and contain tests.

[mgol]

The docs don't really specify what happens if a class appears in both properties. $.effects.animateClass currently applies the options in iteration order from what I understand. And because remove is specified after add, it has precendence.

It's probably too late to change it now and I'm not even sure if that would be desired. I'd advise to just filter out the classes you don't want removing from the second argument.