JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="myframe" src="http://www.w3schools.com"></iframe>
<span id="callback">No Callback</span>
<button id="b" onclick="tt()">
test
</button>

CSS

iframe {
    width:100px;
    height:100px;
}

JavaScript

//function that happens when loaded
function loaded() {
    b.innerHTML = 'Call Basdsdsdck Worked';
};
//gets elements and sets them to variables
var b = document.getElementById('callback')
var a = document.getElementById("myframe");
//listens to load event
a.addEventListener("load", loaded());