Question

How do a I create a validator, which has these simple rules. An expression is valid if

it must start with a letter
it must end with a letter
it can contain a dash (minus sign), but not at start or end of the expression

Answer 1

/^[A-Za-z]+(-?[A-Za-z]+)?$/ 

this seems like what you want.

^ = match the start position
^[A-Za-z]+ = start position is followed by any at least one or more letters.
-? = is there zero or one hyphens (use ‘*’ if there can be multiple hyphens in a row).
[A-Za-z]+ = hyphen is followed by one or more letters
(-?[A-Za-z]+)? = for the case that there is a single letter.
$= match the end position in the string.