JSFiddle - React, Tailwind, and code Playground

HTML

<button id="b1"> 1 </button>
<button id="b2"> 2 </button>

JavaScript

var b1 = document.getElementById("b1");
var b2 = document.getElementById("b2");

b1.onclick = function() {
     b1.style.background = "green";
     b2.style.background = "";   
}

b2.onclick = function() {
     b1.style.background = "";
     b2.style.background = "green";   
}