JSFiddle - React, Tailwind, and code Playground
HTML
<ul class="parent">
<li>L1
<ul>
<li>L2
<ul>
<li>L3</li>
</ul>
</li>
<li>
<ul>
<li>L3
<ul></ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
CSS
.level-1{
background:red;
}
.level-2{
background:green;
}
.level-3{
background:blue;
}
JavaScript
$('.parent ul').addClass(function(){
var cssClass = "level-" + $(this).parents('ul').length;
console.log("attach class:" + cssClass)
return cssClass;
});