Alert user to save before unload

beforeunload.js

$(document).ready(function() {
    // ----------------------------
    // Show message if data have been modified without saving first
    // ----------------------------
    var CHANGED = false;
    window.onbeforeunload = function() {
        return (CHANGED == true ? "Leaving Page with unsaved changes" : null);
    }

    // ----------------------------
    // Store initial input values in DOM data and listen for any changes to modify the CHANGED variable
    // ----------------------------
    $("input, select, textarea").each(function() {
        $.data(this, "lastvalue", $(this).val());
        $(this).bind("keyup keydown keypress change blur", function() {
            CHANGED = $(this).val() !== $.data(this, "lastvalue") ? true : false;
        });
    });

    // ----------------------------
    // Deactivate the window onbeforeload event if the form is submitted
    // ----------------------------
    $('form').submit(function() {
        CHANGED = false;
   });
});