Dealing with unsaved form data when user closes the browser

Question

I'm having hard time trying to figure out how to auto-save user data in a form when the browser is being closed or user changes the page. The onBeforeUnload event is OK when you want to open a dialog box, but by then it's too late to save the changes (except if you just block the browser in the onBeforeUnload handler long enough for it to pass the request to the server...but I'd rather not do that).

I am sure some of you have had to deal with the unsaved form problem. What do you do? Do you:

• let users just lose their changes,
• ask them using a modal window if they are sure they did the right thing,
• save individual fields on the fly as they change,
• or do you have some ultimate method to automagically save the data when it's about to be lost irretrievably?

Answer 1

I like your third option:

• save individual fields on the fly as they change.

I'm having to deal with a similar situation, and that's what we are doing. The two main things that sell that to me:

1. Improved user experience - the user will be impressed by a form that does not lose changes. They are 'committed' once they are validated. E.g., he types in a valid email address, and it is saved instantly, furthermore he is provided some sort of feedback for each field that is successfully been saved (a green tick for example, appears next to the field).
2. No more 'oh crap my browser crashed and I lost all my info' situations.

Disadvantages: The extra man-hours involved in developing such a solution, and the possibly that it ends up not degrading as nicely as a simpler solution. That said, it is still worth it IMO.