JSFiddle - React, Tailwind, and code Playground
HTML
<ul class="parent">
<ul>
<li>
<ul></ul>
</li>
<li>
<ul>
<li>
<ul>
<li>
<ul></ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</ul>
JavaScript
var parent_ul = $('.parent');
var parent_ul_lists = parent_ul.find('ul');
parent_ul_lists.each(function(){
$(this).addClass('level-'+ ($(this).parents().length -1)/2);
});