Apr 16

Preventing User from Leaving the Page with Unsaved Changes

In a WaveMaker app, pages have specific life cycle events. An onBeforePageLeave is a new event that allows you to perform certain checks before the user is about to navigate out of the page. This feature is available since the WaveMaker 10.0 version.

Following are the typical scenarios when this event is invoked:

  • Before you navigate from active page to another page
  • Before you reload the app
  • Or, when you close the app browser tab

Problem Use Case

The app should prevent users from exiting the page before they could:

  • accidentally exit the page while filling up the form
  • Or, navigate away from the active page before they save any changes to the form


With the help of the onBeforePageLeave event, the app developer can add some checks and prevent the user from exiting the page.


You can define the event callback in the page script with the following script:


For a registration form page, the user should get a warning message, if the user has filled in some information and attempts to navigate away from the page. To achieve this, you can write the following lines of code in the page script.

Usage in app.js

If you want to handle multiple pages throughout the app, write the callback event in the app.js file, as below:

Important points to be aware of: 

If the event is defined in app.js as well as on a page, then:

  • the event on the page will be invoked first before the one in app.js.
  • if the page event returns false, the navigation from the page will be prevented and the app.js event will not be invoked.
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