Trigger OnUnload Event

by jacobwsmith

JavaScript

window.onload = function() {
  window.addEventListener("beforeunload", function(e) {
    var confirmationMessage = 'It looks like you have been editing something. ' +
      'If you leave before saving, your changes will be lost.';

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