Minimum 3 characters, all small case, can use maximum of 2 numbers, no special characters allowed. I tried using ^[a-zA-Z0-9]*$ but I'm unable to limit the numbers used

Can someone help me.

CodePudding user response：

You could use a negative lookahead assertion to rule out more than 3 digits:

/^(?!(?:.*\d ){3,})[a-z0-9]{3,}$/

Here is an explanation of the pattern:

• ^ from the start of the string
• (?!(?:.*\d ){3,}) assert that 3 or more digits do NOT occur
• [a-z0-9]{3,} then match 3 or more lowercase letters or digits
• $ end of the string

Here is a working demo.

CodePudding user response：

You could use check if there are at least 3 allowed characters, and then match 0, 1 or 2 digits.

^(?=[A-Za-z\d]{3})[A-Za-z]*(?:\d[A-Za-z]*){0,2}$

Explanation

• ^ Start of string
• (?=[A-Za-z\d]{3}) Positive lookahead, assert 3 allowed chars
• [A-Za-z]* Match optional chars A-Za-z
• (?:\d[A-Za-z]*){0,2} Repeat 0-2 times matching a single digit and optional chars A-Za-z
• $ End of string

See the matches on regex101.