JSFiddle - React, Tailwind, and code Playground

HTML

<div id="category_1">
    <h3 class="maintitle">
        <a class="toggle">..</a>
        <a href="#">Cat 1 Title</a>
    </h3>
    <div>
    </div>
</div>

<div id="category_2">
    <h3 class="maintitle">
        <a class="toggle">..</a>
        <a href="#">Cat 2 Title</a>
    </h3>
    <div>
    </div>
</div>

JavaScript

var catsArray = [1,2];

var cats = $('#category_'+catsArray.join(',#category_'));

console.log(cats);