JSFiddle - React, Tailwind, and code Playground

HTML

<div customAttribute="1" > element 1 </div>
<div customAttribute="1-1" > element 1-1 </div>
<div customAttribute="1-1-1" > element 1-1-1 </div>
<div customAttribute="1-1-2" > element 1-1-2 </div>
<div customAttribute="1-2" > element 1-2 </div>

CSS

div[customAttribute^='1-']:not([customAttribute^='1-1-']) {color: red;}

JavaScript

$("div[customAttribute^='1-']:not([customAttribute^='1-1-'])").css('font-weight', 'bold');