6 characters followed by hyphen(optional) followed by optional 4 characters

Question

I need a regular expression for which:

the string is alphanumeric and have exactly 6 characters in the first half followed by hyphen(optional) followed by optional 4 characters:(cannot have more than 4 characters in the second half)

so any of the following is valid

11111A
111111-1
111111-yy
yyyyy-989
yyyyyy-9090

I thought this expression /[a-zA-Z0-9]([-])?[a-zA-Z0-9]{5,10}$/; should work but I'm unable to get it working correctly.

Answer 1

^[a-zA-Z0-9]{6}(-[A-Za-z0-9]{1,4})?$