JSFiddle - React, Tailwind, and code Playground

HTML

<div id='maindiv'></div>

JavaScript

$(document).ready(function() {
    document.getElementById("maindiv").innerHTML = '<iframe  id="mainf" onload="calcheight(this)" height="100px" name="mainf" src="/echo/html" width="100%" scrolling="no" frameborder="1" ></iframe>';


});

function calcheight(iframeid) {
    if (navigator.appName == 'Netscape') {
        var ht = iframeid.contentWindow.document.body.scrollHeight;
        //var ht = iframeid.contentDocument.documentElement.scrollHeight;
    } else {
        var ht = iframeid.contentWindow.document.body.scrollHeight;
    }
    alert(ht);
}