JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="btn" onclick="javascript:Klik()" value="Press Me!"></input>

JavaScript

function Klik(){
    var destURL = 'http://www.planet-data.eu/sites/default/files/presentations/Big_Data_Tutorial_part4.pdf';
    
    var childWindow = window.open(destURL, "planet-data.eu", "");
    var count = 1;
    var pollTimer = window.setInterval(function () {
            var _div = document.createElement('div');
            _div.innerHTML = childWindow.closed + ' ' + count;
            document.body.appendChild(_div);
            if (childWindow && childWindow.closed && count > 5) {
                window.clearInterval(pollTimer);
                handler();
            }
            count++;
        }, 200);
}
function handler(){
    alert('made it');
}