JSFiddle - React, Tailwind, and code Playground

HTML

<p>Click button to change b style class from DIV. background-color will change from black to blue (hopefully)</p>

<button onclick="myFunction()">Try it</button>

<div id="myDIV" class="my1bla">
  I am a DIV element
</div>

CSS

.my1bla {
  background-color: black;
}

.mybla {
  background-color: blue;
}

JavaScript

function myFunction() {
  var x = document.getElementById("myDIV");

  x.classList.value = x.classList.value.replace("1", "");
}