Take the 2-minute tour ×

I am completely new to regular expressions ,and I am trying to create a regular expression in flex for a validation.

Using a regular expression, I am going to validate that the user input does NOT contain any white-space and consists of only characters and digits... starting with digit.

so far i have:


This correctly checks for user input to start with a character followed by a possible digit, but this does not check if there is white space...(in my tests if user input has a space this input will pass through validation - this is not desired) can someone tell me how I can modify this expression to ensure that user input with whitespace is flagged as invalid?

share|improve this question

3 Answers 3

up vote 7 down vote accepted

You'll need to anchor the regex at the start and end of the string:


makes sure that not just a substring but the entire string is matched by the regex.

share|improve this answer
thanks!! the substring explanation helped a lot =) –  Rees May 16 '10 at 20:48

Try "^[A-Za-z][A-Za-z0-9]*$".

share|improve this answer


In future go with the above link which will be very useful for you.

share|improve this answer

Your Answer


