Detecting Unsaved Changes

In the .aspx page, you need a Javascript function to tell whether or not the form info is "dirty"

<script language="javascript">
    var isDirty = false;

    function setDirty() {
        isDirty = true;
    }

    function checkSave() {
        var sSave;
        if (isDirty == true) {
            sSave = window.confirm("You have some changes that have not been saved. Click OK to save now or CANCEL to continue without saving.");
            if (sSave == true) {
                document.getElementById('__EVENTTARGET').value = 'btnSubmit';
                document.getElementById('__EVENTARGUMENT').value = 'Click';  
                window.document.formName.submit();
            } else {
                 return true;
            }
        }
    }
</script>
<body class="StandardBody" onunload="checkSave()">

and in the codebehind, add the triggers to the input fields as well as resets on the submission/cancel buttons....

btnSubmit.Attributes.Add("onclick", "isDirty = 0;");
btnCancel.Attributes.Add("onclick", "isDirty = 0;");
txtName.Attributes.Add("onchange", "setDirty();");
txtAddress.Attributes.Add("onchange", "setDirty();");
//etc..

Using jQuery:

var _isDirty = false;
$("input[type='text']").change(function(){
  _isDirty = true;
});
// replicate for other input types and selects

Combine with onunload/onbeforeunload methods as required.

From the comments, the following references all input fields, without duplicating code:

$(':input').change(function () {

Using $(":input") refers to all input, textarea, select, and button elements.


One piece of the puzzle:

/**
 * 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;
}

And another:

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.";
  }
};

Wrap it all up, and what do you get?

var confirmExitIfModified = (function() {
  function formIsDirty(form) {
    // ...as above
  }

  return function(form, message) {
    window.onbeforeunload = function(e) {
      e = e || window.event;
      if (formIsDirty(document.forms[form])) {
        // For IE and Firefox
        if (e) {
          e.returnValue = message;
        }
        // For Safari
        return message;
      }
    };
  };
})();

confirmExitIfModified("someForm", "You have unsaved changes.");

You'll probably also want to change the registration of the beforeunload event handler to use LIBRARY_OF_CHOICE's event registration.

Tags:

Javascript

Asp.Net

Prompt

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