JavaScript Regular expression, characters can't be all the same

Asked Oct 21 '22 at 19:58

Active Oct 21 '22 at 19:59

Viewed 17 times

I'm looking for a regex that only allows numbers from 0-9, and letters from a-z or A-Z. No max length. Digits can't be all the same. For example,

Not allowed: 000000 11111111 aaaaaaaaa BBBBB

Allowed: 00000001 11111111112 AAAAAAAAAAAAAB

I've tried /^(?!(.)\1{5})[0-9a-zA-Z]+$/ but looks like it only checks if the first 5 letter repeats.

Is there a way to check the pattern without giving a fixed length?

edited Oct 21 '22 at 19:59

kelsny

asked Oct 21 '22 at 19:58

Yuelin

Do you *have* to use regex or are you open to more typical JS solutions? – kelsny Oct 21 '22 at 19:59
Why not use `^(.)(\1)*$` and negate the result? This matches strings that consist of only one character. – kelsny Oct 21 '22 at 20:05
"Not equal to" rule is `^(?!B$).*`. So, you need `$`, `/^(?!(.)\1{5}$)[0-9a-zA-Z]+$/`. Or, also try `/^(?!(.)\1{5}(?!\1))[0-9a-zA-Z]+$/` – Wiktor Stribiżew Oct 21 '22 at 20:05
@WiktorStribiżew Doesn't `^` match the beginning of the line, though (at least in JavaScript regex)? – kelsny Oct 21 '22 at 20:06
`^` matches the start of string here. – Wiktor Stribiżew Oct 21 '22 at 20:07

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