JSFiddle - React, Tailwind, and code Playground

HTML

<p class="foo" style="background-color: magenta">text</p>
<hr>
<button id="reset">reset</button>

CSS

.foo {
  color: cyan;
}

JavaScript

reset.addEventListener('click', () => {
  document.querySelector('.foo').removeAttribute('style')
  document.querySelector('.foo').removeAttribute('class')
})