Check if Form is Dirty in javascript (You need to check if user changed anything in an HTML form. Below function formIsDirty returns a boolean value true or false depending on weather user modified something within the form.)

1)

/**

 * Determines if a form is dirty by comparing the current value of each element

 * with its default value.

 *

 * @param {Form} form the form to be checked.

 * @return {Boolean} <code>true</code> if the form is dirty, <code>false</code>

 *                   otherwise.

 */

function formIsDirty(form) {

  for (var i = 0; i < form.elements.length; i++) {

    var element = form.elements[i];

    var type = element.type;

    if (type == "checkbox" || type == "radio") {

      if (element.checked != element.defaultChecked) {

        return true;

      }

    }

    else if (type == "hidden" || type == "password" ||

             type == "text" || type == "textarea") {

      if (element.value != element.defaultValue) {

        return true;

      }

    }

    else if (type == "select-one" || type == "select-multiple") {

      for (var j = 0; j < element.options.length; j++) {

        if (element.options[j].selected !=

            element.options[j].defaultSelected) {

          return true;

        }

      }

    }

  }

  return false;

}




2)




window.onbeforeunload = function(e) {

  e = e || window.event; 

  if (formIsDirty(document.forms["someForm"])) {

    // For IE and Firefox

    if (e) {

      e.returnValue = "You have unsaved changes.";

    }

    // For Safari

    return "You have unsaved changes.";

  }

};