Regular expression to validate the given input which accepts one space or Hyphen which is part of th-CodePudding

In the below example, I am validating the 4 characters' text with include either one space or Hyphen (-) or without that also only 4 characters.

Regex : ^[A-Z0-9]{4}$|(?=^.{4}$)^[A-Z0-9] [- ]?[A-Z0-9] $

It worked the cases as below cases but it failed to validate the text contains all same characters like 1111, AAAA is not allowed

1234  valid
12-4  valid
12 4  valid  
1111  invalid ( as all are the same characters)
11-1  invalid ( as all are the same characters)
12345 invalid

CodePudding user response：

You can use this regex to match your strings:

^(?=[A-Z0-9] [ -]?[A-Z0-9] )(?!([A-Z0-9])(?:\1|[ -]){3}).{4}$

Regex explanation:

^ start of string
(?=[A-Z0-9] [ -]?[A-Z0-9] ) asserts that the string consists of one or more of A-Z0-9, an optional or -, and one or more of A-Z0-9
(?!([A-Z0-9])(?:\1|[ -]){3}) asserts that the first character is not repeated in every position where there is a character
.{4}$ matches only 4 characters between start and end of string