JSFiddle - React, Tailwind, and code Playground

HTML

<p><button id="btn1">Click me</button></p>
<p><button id="btn2">Click me as well</button></p>

JavaScript

function clickHandler(e) {
    alert(e);
}

window.onload = function() {
    document.getElementById('btn1').onclick = clickHandler;
    document.getElementById('btn2').onclick = function(e) {
        clickHandler(e);
    }
}