How to get the "Leave site? Changes that you made may not be saved" when trying to close a window with a populated form

Question

I have a form that when filled in, I can exit the window without being given a warning (I'm using Chrome).

How can I ensure I get a warning before exiting? Is there a Django setting for this?

Django is server side. It doesn’t know what form data has or hasn’t been entered by a user until the form is submitted. This is a client side problem, and would require JavaScript. — fubar, Aug 04 '18 at 01:29
Does this answer your question? [Best way to detect when a user leaves a web page?](https://stackoverflow.com/questions/147636/best-way-to-detect-when-a-user-leaves-a-web-page) — ggorlen, Jan 04 '20 at 13:52

davidchoo12 · Accepted Answer · 2020-10-09T07:45:32.870

20

You need to supply a function returning a string to onbeforeunload of the window or the document body in order to trigger the "Leave site" popup.

window.onbeforeunload = () => '';

<a href="http://example.com">Click to trigger</a>

edited Oct 09 '20 at 07:45

answered Aug 04 '18 at 01:55

davidchoo12

Getting this error when I paste in my js file: https://i.imgur.com/RzGwvyt.png any idea? – Zorgan Aug 04 '18 at 02:51
Nevermind it is working. However are you able to tell me how I can only summon the popup when the form is not empty? currently it pops up every time I navigate away from any page... – Zorgan Aug 04 '18 at 02:52
You can add a condition to check if any of the form input is empty then return a string else return null – davidchoo12 Aug 05 '18 at 13:02
Probably you had that because your editor does not support arrow functions. In my editor, for example, I can choose compatible javascript standard. I assume you have something similar. – Sharikov Vladislav Oct 29 '21 at 06:14

score 3 · Answer 2 · answered Aug 04 '18 at 01:40

3

The event is called beforeunload, so you can assign a function to window.onbeforeunload

answered Aug 04 '18 at 01:40

Scath

2 Answers2