JSFiddle - React, Tailwind, and code Playground
HTML
<h1>My Web Page</h1>
<p id="demo">A Paragraph</p>
<button type="button" id='btn1'>Try it</button>JavaScript
var btn = document.getElementsByTagName('button');
console.log(btn);
btn.onclick=function(){
alert('entered');
document.getElementById("demo").innerHTML="test";
}