Regular Expression Repeating Pattern separated by comma

 

I have a regular expression of the following: 

.regex(/^(?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{4})$/)

Must be exactly 4 characters Must contain at least 1 numeric and 1 alpha

Although I rarely do regular expression, this was relatively easy. I now have a new requirement that I have tried to implement, but cannot get right.

New requirement: Be able to have a comma separated list of the same type of input as before. Cannot end with a comma. Each item must be valid per the rules above (4 characters, at least on numeric, at least one alpha) 

Valid:  123F,U6Y7,OOO8
Invalid:  Q2R4,
Invalid:  Q2R4,1234
Invalid:  Q2R4,ABCD
Invalid:  Q2R4,N6

I very much appreciate your help! Thanks!

Some of the other answers are repeating the lookahead assertions. That's not necessary.

Here's a regular expression that matches a comma-separated sequence of atoms, where each atom is four alphanumeric characters: 

^[A-Z0-9]{4}(?:,[A-Z0-9]{4})*$

Of course, that's not quite what you want. You don't want atoms that are all alphabetic. Here's a negative lookahead assertion that prevents matching such an atom anywhere in the text: 

(?!.*[A-Z]{4})

And you don't want atoms that are all numeric either: 

(?!.*[0-9]{4})

Putting it all together: 

^(?!.*[A-Z]{4})(?!.*[0-9]{4})[A-Z0-9]{4}(?:,[A-Z0-9]{4})*$

This regex should work: 

^(?:(?![0-9]*,)(?![a-zA-Z]*,)[a-zA-Z0-9]{4},)*(?![0-9]*$)(?![a-zA-Z]*$)[a-zA-Z0-9]{4}$

Or you can shorten [0-9] to d . It doesn't really matter, though, since the expanded code can be more readable. 

^(?:(?!d*,)(?![a-zA-Z]*,)[a-zA-Zd]{4},)*(?!d*$)(?![a-zA-Z]*$)[a-zA-Zd]{4}$

You can see how your regex is transformed to make this regex, when I line it up like below: 

^
(?:
  (?!d*,)(?![a-zA-Z]*,)[a-zA-Zd]{4},
)*
  (?!d*$)(?![a-zA-Z]*$)[a-zA-Zd]{4}
$

Try using this regex (regex test): 

.regex(/^(?:(?![0-9]{4}|[a-zA-Z]{4})[a-zA-Z0-9]{4})(?:(?:b,)(?![0-9]{4}|[a-zA-Z]{4})[a-zA-Z0-9]{4})*$/)

Explanation:

  • (?:b,) -> Match with a , at the beginning of the string only if its preceded by a word boundary

  • (?:(?![0-9]{4}|[a-zA-Z]{4})[a-zA-Z0-9]{4}) -> Match a string with letter and digits only if dont have 4 digits ow 4 letters

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