JSFiddle - React, Tailwind, and code Playground

HTML

<span class="sdt_descr">a1</span>
<span class="sdt_descr">b1</span>
<span class="sdt_descr">c1</span>
<span class="sdt_descr">a3</span>

CSS

.foo{
color:red;
}

JavaScript

var list = ["a1", "a2", "a3"];
    
    var joined_list = list.join(',.'); //turn into string
    // you need to add a "#" to the beginning of the string to make a proper selector
    $('.'+joined_list).addClass('foo');