JSFiddle - React, Tailwind, and code Playground

HTML

blah blah
<span id="message" style="color:red;"></span>

JavaScript

window.addEventListener("beforeunload", function (e) {
  var confirmationMessage = "\o/";

  (e || window.event).returnValue = confirmationMessage;     //Gecko + IE
  return confirmationMessage;                                //Webkit, Safari, Chrome etc.
}, true);

window.addEventListener("beforeunload", function( event ) {
  event.returnValue = "\o/";
}, true);

//is equivalent to
window.addEventListener("beforeunload", function( event ) {
  event.preventDefault();
}, true);