JSFiddle - React, Tailwind, and code Playground

HTML

<button class="btn active">a</button>
<button class="btn">b</button>
<button class="btn">c</button>

CSS

.active { color: red; }

JavaScript

$(".btn").on('click', function(){
    $(this).siblings().removeClass('active')
           .end()
           .addClass('active');
});