JAVASCRIPT

window on close event javascript?

// JavaScript event for when the user closes the window.
window.onbeforeunload = () => {
  return "Do you really want to close?";
};

window close function in javascript

var win = window.open("http://www.google.com");

var winClosed = setInterval(function () {

    if (win.closed) {
        clearInterval(winClosed);
        foo(); //Call your function here
    }

}, 250);