write an ng-pattern to disallow whitespaces and special characters

Question

I am trying to get an angular ng-pattern to check that a username has no whitespaces or special characters. The following form return false if you enter whitespaces or special c

Answer 1

To surface the specific answer I was looking for, I already had the pattern suggested by Sniffer /^[a-zA-Z0-9]*$/, but angular still appeared to ignore leading/trailing whitespace. As Cristian mentions in the comments:

Angular will trim the input model, meaning that the validation doesn't trigger for spaces. You can add an ng-trim="false" to the input to fix this.

Note that Angular is trying to protect you by silently trimming whitespace by default. In my case, I want the user to be aware that the trailing whitespace is invalid.