JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li id="cat-12">
        <span id="subcat-13">lorem</span>
        <span id="subcat-43">ipsum</span>
    </li>
    <li id="cat-41">
        <span id="subcat-22">lorem</span>
        <span id="subcat-23">ipsum</span>
    </li>
</ul>

JavaScript

var arr = $('ul li span').map(function(){
   return $(this).attr('id');
});

console.log(arr);