When should forms be cleaned?

Question

By "cleaned" I mean formatting inputs such as "a1b2c3" into "A1B 2C3" or "5551234567" into "(555) 123-4567". I figure we have few options:

1. As the user is typing. For instance, when a user is typing a postal code, all letters are instantly capitalized, or after the user types 3 digits of a phone number, it puts brackets around them.
2. When the field loses focus.
3. Never. Formatting happens on the server-side only, just before it is inserted into the DB. The user never gets to see how it was formatted unless it is displayed on the site somewhere.
   (3b) If there were form errors, or on the confirmation page. If there are form errors and the form needs to be re-displayed, the formatting on the valid inputs will appear, or if you have a confirmation page (are these inputs correct?) they will show there.
4. Never ever. Data should be dumped into the database as-is and only formatted in the template/view just before it is displayed back to the user.

What do you think? I think I like (2). Reminds me of how code-formatting works in Visual Studio (happens when you close a brace or type a semi-colon).

Answer 1

I'd go with either (1) or (2), depending on the kind of input. (1) is probably most user-friendly if done right, but it will be more complex to implement neatly (e.g., what happens if I delete a digit from a hyphenated phone number - or a hyphen?). Go with (1) if you can afford it, otherwise (2).

Answer 2

I follow the same method I use for validation. Once on the client side, once on the server side. Whether it happens on loose focus or as they type it doesn't really matter.