Javascript regular expression to check whether a string is a combination of certain character

Question

I want to check if a string starting from - ie hypen followed by any combination of the 3 characters ie a , p or m .

For example: -a , -p , -ap,-am,-apm etc.

Please help.

Answer 1

Use the following regex . This will check if the str starts with - and followed by any one of the a , p or m in any sequence having at least one character and maximum of three characters.

/^-[apm]{1,3}$/.test(str)

Regex Explanation

1. / : Delimiter of regex
2. ^- : Starts with -
3. [apm] : Matches any characters inside [] in any sequence
4. {1,3} : Matches preceding set of characters in the range from 1 to 3
5. $ : End of the match