This example shows how to load tab contents using htmx, and to select the "active" tab using Javascript. This reduces some duplication by offloading some of the work of re-rendering the tab HTML from your application server to your clients' browsers.
You may also consider a more idiomatic approach that follows the principle of Hypertext As The Engine Of Application State..
The HTML below displays a list of tabs, with added HTMX to dynamically load each tab pane from the server. A simple hyperscript event handler uses the take
command to switch the selected tab when the content is swapped into the DOM. Alternatively, this could be accomplished with a slightly longer Javascript event handler.
<div id="tabs" hx-target="#tab-contents" _="on htmx:afterOnLoad take .selected for event.target">
<a hx-get="/tab1" class="selected">Tab 1</a>
<a hx-get="/tab2">Tab 2</a>
<a hx-get="/tab3">Tab 3</a>
</div>
<div id="tab-contents" hx-get="/tab1" hx-trigger="load"></div>