JSFiddle - React, Tailwind, and code Playground

HTML

<button id='click'>click me</button>

<iframe style="display:none" id='MainPopupIframe' src='' /></iframe>

JavaScript

window.onload=function(){
    var ifr=document.getElementById('MainPopupIframe');
    ifr.onload=function(){
        this.style.display='block';
        console.log('laod the iframe')
    };
    var btn=document.getElementById('click');    
    btn.onclick=function(){
        ifr.src='http://heera.it';    
    };
};