I allow only one hyphen (-) in regex

Question

I have a text box where i get the last name of user. How do I allow only one hyphen (-) in a regular expression?

^([a-z A-Z]*-){1}[a-z A-Z]*$

Answer 1

you can use negative lookahead to reject strings having more than one hyphen:

^(?![^-]+-[^-]+-)[a-zA-Z- ]+$

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Matched demo on debuggex.

Another Matched demo on debuggex.

Not Matched Demo demo on debuggex.

Answer 2

Your regular expression allow exactly one -. but I assume that you want to mach "Smith", "Smith-Kennedy", but not "Smith-", to do this you just must move the hyphen to the second group:

^[a-z A-Z]+(-[a-z A-Z]+)?$

BTW, in almost all cases when * is used + is the better solution.

Answer 3

I am assuming you want up to 1 hyphen. If so, the regex you want is

^[a-z A-Z]*-?[a-z A-Z]*$

You can visualize it on www.debuggex.com.

Answer 4

A problem with your regex is that it forces the user to put a -. You can use ? to make it optional :

^[a-z A-Z]*\-?[a-zA-Z]*$

Answer 5

If it matches .*-.*-, then you have more than one hyphen and such string should not be accepted