Unmatch when Slash( / ) is followed by Underscore( _ ) or hyphen(

I am constructing an ID, in Javascript, which doesn't allow special character and uppercase letter. We could have / _ - in the ID, but the it should not begin with these.

hello correct
helloWorld incorrect
123hello correct
hello/world correct
-hello incorrect
_hello incorrect
$hello incorrect
/hello incorrect
hello$ incorrect
hello_world correct
hello-world correct
hello-world/apple correct
hello_world/apple correct
hello_world/apple123 correct

I have the following regEx which almost handles all the cases, however there is one case where if slash(/) is present it should not be followed by hyphen(-) or underscore(_), which i am unable to solve

^(?=.{1,50}$)(([a-z0-9]) ([-_/a-z0-9])*)$

hello_world/-apple incorrect
hello_world/_apple incorrect
hello_world//apple incorrect

Any help on this would be much appreciated.

CodePudding user response：

You can use

^(?=.{1,50}$)[a-z0-9] (?:[-_\/][a-z0-9] )*[-_\/]?$

See the regex demo.

Details:

^ - string start
(?=.{1,50}$) - there can only be 1 to 50 chars in the string
[a-z0-9] - one or more lowercase ASCII letters or digits
(?:[-_\/][a-z0-9] )* - zero or more sequences of
- [-_\/] - a -, _ or / char
- [a-z0-9] - one or more lowercase ASCII letters or digits
[-_\/]? - an optional -, _ or / char
$ - end of string.