The class-tools extension allows you to specify CSS classes that will be swapped onto or off of the elements by using a classes or data-classes attribute. This functionality allows you to apply CSS Transitions to your HTML without resorting to javascript.
A classes attribute value consists of “runs”, which are separated by an & character. All class operations within a given run will be applied sequentially, with the delay specified.
Within a run, a , character separates distinct class operations.
A class operation is an operation name add, remove, or toggle, followed by a CSS class name, optionally followed by a colon : and a time delay.
Install
<script src="https://unpkg.com/htmx.org/dist/ext/class-tools.js"></script>
Usage
<div hx-ext="class-tools">
<div classes="add foo"/>
<div class="bar" classes="remove bar:1s"/>
<div class="bar" classes="remove bar:1s, add foo:1s"/>
<div class="bar" classes="remove bar:1s & add foo:1s"/>
<div classes="toggle foo:1s"/>
</div>
[HTMX Reference](https://htmx.org/extensions/class-tools/)