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}$)(([a-z0-9])+([-_/a-z0-9])*)$

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

Any help on this would be much appreciated.

>Solution :

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.