had a colleague come to me recently for help on a client issue. The customer wanted two things; the first was to set up the capability to warn users when they were navigating away from a modified form without saving it, but to do this only on selected forms rather than globally. The second was to modify the text included in the alert dialog to be whatever they wanted. In this post I’ll explain some of the options that ServiceNow provides in this area and how you can get even more flexibility and control over this behavior through scripting.

Custom Dirty Form Alert

The first thing to know about this functionality is that its main purpose is to identify that fields on a form have been modified, and alert the user if they try to navigate away from one of these forms if the record hasn’t been saved. I’ve touched on this topic before in an article I wrote about identifying modified fields. Because this is a common problem, ServiceNow actually includes a property (which is active by default) to present this alert. You’ve probably noticed this alert as you’ve worked in your ServiceNow instance…

Default Dirty Form Alert

The name of the property that controls this behavior is ‘glide.ui.dirty_form_support’ and can be changed by accessing the property through the ‘sys_properties’ table. This property works globally across an instance and causes the alert to display for any standard forms (meaning this isn’t going to work in the service catalog) so there’s not a whole lot you can do to control the functionality. One thing you can do easily is control part of the message contained in the alert. I say “part” because the dialog is actually a standard javascript/browser behavior so that limits your control a bit. The part you can customize is the line in the alert that looks like this…

Changes have been made. Continuing will discard the changes.

This text is actually accessed via a ‘Message’ record in the system that is passed from the server to the client when a form is rendered. You can find and modify this global message by navigating to ‘System UI -> Messages’ and looking for the entry as shown here…

Dirty Form Alert Message

Beyond the basics…

While the information above is useful, it still doesn’t solve the issues I described above…warning ONLY on selected forms to selected users, and controlling the text on these selective dialogs. As is often the case, a carefully-crafted client script can provide the needed flexibility.

When a form loads in your browser, it comes with a ‘window.onbeforeunload’ object that detects when the window is closed or navigated away from. In most cases there’s nothing associated with this event, but in cases like this, you can trigger specific things (like an alert). The way this works is kind of unique for javascript event handlers. In this case, the ‘window.onbeforeunload’ event gets attached to a function whose purpose is to return text to be inserted into the alert dialog. By attaching a function to this event in a client script you can override the default message and apply the message and alert selectively across different forms and for different roles and users.

The script below is the simplest example but you can add client-side checks for roles and other things if you want. All you have to do is change the ‘YOUR CUSTOM MESSAGE HERE’ line to

Please note that this client script is an override of the dirty form system property described above. If the system property is active, then it will behave normally for any form that doesn’t include a custom client script. The client script also has no access to the message record described above so the alert message is defined within the script itself.
‘Custom Dirty From Alert’
Name: Custom Dirty From Alert
Table: Wherever you want!
Type: onLoad

function onLoad() {
   //Add the 'onbeforeunload' event
   window.onbeforeunload = function() {
      //If we're leaving a modified form without a submit
      if (!g_form.submitted && g_form.modified) {
         //Add the custom dialog message here
         return 'YOUR CUSTOM MESSAGE HERE.';

Custom Dirty Form Alert