JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>one</li>
    <li class='activity'>two</li>
    <li>three</li>
</ul>

JavaScript

var but = document.querySelectorAll('ul li'),
    search = document.querySelector('ul .activity');
search.classList.remove('activity');//это выполняет 1 функция...
console.log(search);