Detecting Unsaved Changes

Question

I have a requirement to implement an "Unsaved Changes" prompt in an ASP .Net application. If a user modifies controls on a web form, and attempts to navigate away before saving, a prompt should appear warning them that they have unsaved changes, and give them the option to cancel and stay on the current page. The prompt should not display if the user hasn't touched any of the controls.

Ideally I'd like to implement this in JavaScript, but before I go down the path of rolling my own code, are there any existing frameworks or recommended design patterns for achieving this? Ideally I'd like something that can easily be reused across multiple pages with minimal changes.

I am interested in the same, just not for asp.net, but I think there is a general solution out there. — Michael Neale, Oct 01 '08 at 00:50
The solution I posted below can be used in plain HTML/Javscript. Simply change the "codebehind" to attributes in the HTML tags themselves. — Wayne, Oct 01 '08 at 00:53
I know I'm 5 years late here, but I think I can improve on the previous solutions... I just fixed and updated my answer below. — skibulk, Oct 23 '13 at 21:35

score 100 · Accepted Answer · edited Apr 06 '14 at 20:25

100

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.

edited Apr 06 '14 at 20:25

Dave Jarvis

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answered Oct 01 '08 at 01:26

Aaron Powell

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33

Upvote because I used this solution but there is a slightly easier way. If you use: $(':input').change(function () { then that works for all input fields, you don't need to replicate for other input types. $(":input") selects all input, textarea, select and button elements. – CodeClimber Jul 29 '11 at 08:55
5

I think this may have issues in Firefox. If a user modifies the form, then clicks the browsers Refresh-button, the page will be reloaded and Firefox will populate the form with the users previous entries - without firing the change-event. Now the form will be dirty, but the flag won't be set unless the user makes another edit. – Oskar Berggren Aug 31 '14 at 16:05
9

Just a hint. If form is dirty it still doesn't mean that it contains really changed data. For better usability you have to actually compare old data with the new one ;) – Slava Fomin II Oct 13 '14 at 11:36
Take in mind that `change` for text-inputs triggers once on on leaving / losing focus, whereas [`input`](https://developer.mozilla.org/en-US/docs/Web/Events/input) triggers for every keystroke. (I usually use it alongside `change` with JQuery's [`one()`](http://api.jquery.com/one/), in order to prevent multiple events.) – SpazzMarticus Oct 24 '18 at 10:59

Jonny Buchanan · Answer 2 · 2011-12-12T20:28:48.947

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.

In Firefox 9.0.1 I don't get any message. I have a default message saying "Are you sure you want to leave the page? Some data might be lost" (This is more or less the translation of the message my non-English browser displays to me) — Romain Guidoux, Dec 29 '11 at 17:35
This script is awesome, but for me it also displayed the warning message upon submitting my form. I fixed this by unbinding the event in an onClick (`onclick="window.onbeforeunload=null"`) — Joost, May 14 '14 at 06:29
I like the approach of comparing defaultValue etc properties rather than setting a dirty bit. This means that if someone changes a field, then changes it back, then the form will not report as dirty. — thelem, Jun 26 '14 at 15:04
Thanks, this is great. Can you please tell us how to register for jquery? Unless i have this script on same html page, it does not fire. If i have it inside an external .js file, it does not work. — Shiva Naru, Nov 17 '15 at 19:26

score 17 · Answer 3 · edited Dec 09 '15 at 08:43

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..

score 9 · Answer 4 · edited Feb 02 '11 at 17:06

The following uses the browser's onbeforeunload function and jquery to capture any onchange event. IT also looks for any submit or reset buttons to reset the flag indicating changes have occurred.

dataChanged = 0;     // global variable flags unsaved changes      

function bindForChange(){    
     $('input,checkbox,textarea,radio,select').bind('change',function(event) { dataChanged = 1})
     $(':reset,:submit').bind('click',function(event) { dataChanged = 0 })
}


function askConfirm(){  
    if (dataChanged){ 
        return "You have some unsaved changes.  Press OK to continue without saving." 
    }
}

window.onbeforeunload = askConfirm;
window.onload = bindForChange;

Hi colin reset didn't work when i placed a check box, initially I checked it and unchecked again but alert is getting fired, how can i reset when user unchecked the check box — Developer, Nov 02 '12 at 10:28

score 8 · Answer 5 · answered Oct 01 '08 at 23:45

Thanks for the replies everyone. I ended up implementing a solution using JQuery and the Protect-Data plug-in. This allows me to automatically apply monitoring to all controls on a page.

There are a few caveats however, especially when dealing with an ASP .Net application:

When a user chooses the cancel option, the doPostBack function will throw a JavaScript error. I had to manually put a try-catch around the .submit call within doPostBack to suppress it.
On some pages, a user could perform an action that performs a postback to the same page, but isn't a save. This results in any JavaScript logic resetting, so it thinks nothing has changed after the postback when something may have. I had to implement a hidden textbox that gets posted back with the page, and is used to hold a simple boolean value indicating whether the data is dirty. This gets persisted across postbacks.
You may want some postbacks on the page to not trigger the dialog, such as a Save button. In this case, you can use JQuery to add an OnClick function which sets window.onbeforeunload to null.

Hopefully this is helpful for anyone else who has to implement something similar.

MhdSyrwan · Answer 6 · 2016-01-11T13:18:03.923

7

General Solution Supporting multiple forms in a given page (Just copy and paste in your project)

$(document).ready(function() {
    $('form :input').change(function() {
        $(this).closest('form').addClass('form-dirty');
    });

    $(window).bind('beforeunload', function() {
        if($('form:not(.ignore-changes).form-dirty').length > 0) {
            return 'You have unsaved changes, are you sure you want to discard them?';
        }
    });

    $('form').bind('submit',function() {
        $(this).closest('form').removeClass('form-dirty');
        return true;
    });
});

Note: This solution is combined from others' solutions to create a general integrated solution.

Features:

Just copy and paste into your app.
Supports Multiple Forms.
You can style or make actions dirty forms, since they've the class "form-dirty".
You can exclude some forms by adding the class 'ignore-changes'.

edited Jan 11 '16 at 13:18

answered May 21 '15 at 12:57

MhdSyrwan

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This works well, but I replace the added classes with the `_isDirty` variable as described by Aaron Powell . I didn't see the need to adding and removing classes from the HTML instead of variables in the javascript. – Martin Jan 06 '16 at 16:58
1

The idea of using html classes here is to attach the 'dirty' attribute with each form since you can't simply use variables to make a general application-wize js/html solution. – MhdSyrwan Jan 07 '16 at 07:55
1

In other words, using a variable will work only for a single form, otherwise you will need an array of dirty flags which will make the solution much more complicated. – MhdSyrwan Jan 07 '16 at 07:55
1

Thanks for explaining that point. My need was only with a single form page. – Martin Jan 07 '16 at 15:18
This is brilliant! Worked as-is. I recommend this. Only thing is: the beforeunload return does not display a user friendly message (as least in most browsers) - any suggestion on how to display a more user friendly message ? – Frank Monroe Jan 16 '21 at 22:49
according to this, https://stackoverflow.com/questions/38879742/is-it-possible-to-display-a-custom-message-in-the-beforeunload-popup, you cannot put a custom message anymore – MhdSyrwan Jan 23 '21 at 16:17
I think it has been removed to protect users from scam sites trying to keep them in by displaying misleading messages trying to encourage them to continue some malicious routine. – MhdSyrwan Jan 23 '21 at 16:20

skibulk · Answer 7 · 2013-10-23T21:37:54.260

Here's a javascript / jquery solution that is simple. It accounts for "undos" by the user, it is encapsulated within a function for ease of application, and it doesn't misfire on submit. Just call the function and pass the ID of your form.

This function serializes the form once when the page is loaded, and again before the user leaves the page. If the two form states are different, the prompt is shown.

Try it out: http://jsfiddle.net/skibulk/Ydt7Y/

function formUnloadPrompt(formSelector) {
    var formA = $(formSelector).serialize(), formB, formSubmit = false;

    // Detect Form Submit
    $(formSelector).submit( function(){
        formSubmit = true;
    });

    // Handle Form Unload    
    window.onbeforeunload = function(){
        if (formSubmit) return;
        formB = $(formSelector).serialize();
        if (formA != formB) return "Your changes have not been saved.";
    };
}

$(function(){
    formUnloadPrompt('form');
});

I tried your approach. It works for Chrome and Firefox, but cannot make it work for Safari on Ipad Mini.. — Dimitry K, Jun 04 '14 at 14:47

score 6 · Answer 8 · answered May 25 '09 at 09:17

The following solution works for prototype (tested in FF, IE 6 and Safari). It uses a generic form observer (which fires form:changed when any fields of the form have been modified), which you can use for other stuff as well.

/* use this function to announce changes from your own scripts/event handlers.
 * Example: onClick="makeDirty($(this).up('form'));"
 */
function makeDirty(form) {
    form.fire("form:changed");
}

function handleChange(form, event) {
    makeDirty(form);
}

/* generic form observer, ensure that form:changed is being fired whenever
 * a field is being changed in that particular for
 */
function setupFormChangeObserver(form) {
    var handler = handleChange.curry(form);

    form.getElements().each(function (element) {
        element.observe("change", handler);
    });
}

/* installs a form protector to a form marked with class 'protectForm' */
function setupProtectForm() {
    var form = $$("form.protectForm").first();

    /* abort if no form */
    if (!form) return;

    setupFormChangeObserver(form);

    var dirty = false;
    form.observe("form:changed", function(event) {
        dirty = true;
    });

    /* submitting the form makes the form clean again */
    form.observe("submit", function(event) {
        dirty = false;
    });

    /* unfortunatly a propper event handler doesn't appear to work with IE and Safari */
    window.onbeforeunload = function(event) {
        if (dirty) {
            return "There are unsaved changes, they will be lost if you leave now.";
        }
    };
}

document.observe("dom:loaded", setupProtectForm);

score 4 · Answer 9 · answered Apr 30 '12 at 19:35

I recently contributed to an open source jQuery plugin called dirtyForms.

The plugin is designed to work with dynamically added HTML, supports multiple forms, can support virtually any dialog framework, falls back to the browser beforeunload dialog, has a pluggable helper framework to support getting dirty status from custom editors (a tinyMCE plugin is included), works within iFrames, and the dirty status can be set or reset at will.

https://github.com/snikch/jquery.dirtyforms

score 4 · Answer 10 · answered Dec 15 '14 at 10:48

Detect form changes with using jQuery is very simple:

var formInitVal = $('#formId').serialize(); // detect form init value after form is displayed

// check for form changes
if ($('#formId').serialize() != formInitVal) {
    // show confirmation alert
}

score 2 · Answer 11 · answered Jul 08 '14 at 06:10

      var unsaved = false;
    $(":input").change(function () {         
        unsaved = true;
    });

    function unloadPage() {         
        if (unsaved) {             
          alert("You have unsaved changes on this page. Do you want to leave this page and discard your changes or stay on this page?");
        }
    }

window.onbeforeunload = unloadPage;

score 2 · Answer 12 · answered Feb 14 '12 at 05:17

I expanded on Slace's suggestion above, to include most editable elements and also excluding certain elements (with a CSS style called "srSearch" here) from causing the dirty flag to be set.

<script type="text/javascript">
        var _isDirty = false;
        $(document).ready(function () {            

            // Set exclude CSS class on radio-button list elements
            $('table.srSearch input:radio').addClass("srSearch");

            $("input[type='text'],input[type='radio'],select,textarea").not(".srSearch").change(function () {
                _isDirty = true;
            });
        });

        $(window).bind('beforeunload', function () {
            if (_isDirty) {
                return 'You have unsaved changes.';
            }
        });

score 1 · Answer 13 · answered Oct 02 '08 at 01:32

This is exactly what the Fleegix.js plugin fleegix.form.diff (http://js.fleegix.org/plugins/form/diff) was created for. Serialize the initial state of the form on load using fleegix.form.toObject (http://js.fleegix.org/ref#fleegix.form.toObject) and save it in a variable, then compare with the current state using fleegix.form.diff on unload. Easy as pie.

darryn.ten · Answer 14 · 2020-11-17T08:17:02.693

1

A lot of outdated answers so here's something a little more modern.

ES6

let dirty = false
document.querySelectorAll('form').forEach(e => e.onchange = () => dirty = true)

edited Nov 17 '20 at 08:17

answered Nov 17 '20 at 08:10

darryn.ten

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3
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score 0 · Answer 15 · answered Oct 01 '08 at 00:56

One method, using arrays to hold the variables so changes can be tracked.

Here's a very simple method to detect changes, but the rest isn't as elegant.

Another method which is fairly simple and small, from Farfetched Blog:

<body onLoad="lookForChanges()" onBeforeUnload="return warnOfUnsavedChanges()">
<form>
<select name=a multiple>
 <option value=1>1
 <option value=2>2
 <option value=3>3
</select>
<input name=b value=123>
<input type=submit>
</form>

<script>
var changed = 0;
function recordChange() {
 changed = 1;
}
function recordChangeIfChangeKey(myevent) {
 if (myevent.which && !myevent.ctrlKey && !myevent.ctrlKey)
  recordChange(myevent);
}
function ignoreChange() {
 changed = 0;
}
function lookForChanges() {
 var origfunc;
 for (i = 0; i < document.forms.length; i++) {
  for (j = 0; j < document.forms[i].elements.length; j++) {
   var formField=document.forms[i].elements[j];
   var formFieldType=formField.type.toLowerCase();
   if (formFieldType == 'checkbox' || formFieldType == 'radio') {
    addHandler(formField, 'click', recordChange);
   } else if (formFieldType == 'text' || formFieldType == 'textarea') {
    if (formField.attachEvent) {
     addHandler(formField, 'keypress', recordChange);
    } else {
     addHandler(formField, 'keypress', recordChangeIfChangeKey);
    }
   } else if (formFieldType == 'select-multiple' || formFieldType == 'select-one') {
    addHandler(formField, 'change', recordChange);
   }
  }
  addHandler(document.forms[i], 'submit', ignoreChange);
 }
}
function warnOfUnsavedChanges() {
 if (changed) {
  if ("event" in window) //ie
   event.returnValue = 'You have unsaved changes on this page, which will be discarded if you leave now. Click "Cancel" in order to save them first.';
  else //netscape
   return false;
 }
}
function addHandler(target, eventName, handler) {
 if (target.attachEvent) {
  target.attachEvent('on'+eventName, handler);
 } else {
  target.addEventListener(eventName, handler, false);
 }
}
</script>

score 0 · Answer 16 · answered Jul 06 '15 at 06:04

In IE document.ready will not work properly it will update the values of input.

so we need to bind load event inside the document.ready function that will handle for IE browser also.

below is the code you should put inside the document.ready function.

 $(document).ready(function () {
   $(window).bind("load", function () { 
    $("input, select").change(function () {});
   });
});

score 0 · Answer 17 · edited Sep 28 '22 at 12:24

I have found that this one works in Chrome with an exception... The messages being returned do not match those in the script:

dataChanged = 0; // global variable flags unsaved changes

function bindForChange() {
  $("input,checkbox,textarea,radio,select").bind("change", function (_event) {
    dataChanged = 1;
  });
  $(":reset,:submit").bind("click", function (_event) {
    dataChanged = 0;
  });
}

function askConfirm() {
  if (dataChanged) {
    var message =
      "You have some unsaved changes.  Press OK to continue without saving.";
    return message;
  }
}

window.onbeforeunload = askConfirm;

window.onload = bindForChange;

The messages returned seem to be triggered by the specific type of action I'm performing. A RELOAD displays a question "Reload Site? And a windows close returns a "Leave Site?" message.

Detecting Unsaved Changes

17 Answers17

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