I've got a job posted at joomlancers for this request. Or if someone here has the skills I'd be willing to pay a few bucks for this.

I've been wasting a lot of my personal time with my very limited php abilities. I've found javascript which will restrict the characters and size for a form field, but implementing it into CB is beyond my abilities now.

The goal:

Restrict username field length.
Not allow spaces in username.
Only allow text and numbers in username, no other characters.

Bad username: "fred smith" or "fred@mail.com"
Good username: "fredsmith"

I think a CB plug would be best for this, with a back end which allows one to configure the username length.

Ultimately this would be nice as a built in CB function.

I've been blown away by the responses....

Necessity is the mother of invention.

I hacked cb and now have achieved this vor now. No my new registrations can't have any characters other than alphabet and numbers...

What is your solution to limiting the username length?

I created a little javascript which only allows numbers and letters in the username field. If they type in something else, or even a space, a popup comes up and tells them they need to redo it and it wipes out the text they put in the field.

I'm no pro. I did an "onkeyup" to trigger the javascript so I had to disable username checking which also works on key up.

I also put maxlength="16" in there to restrict the username to 16 characters.

Attached is a .zip file of my cb.core.php file which has everything working.

You can see it in action on the registration page of www.thegolfspace.com or www.themacspace.com