I need a regex to invalidate all the same digits in a phone number

Question

The regex should invalidate the phone number if all the digits are same. For eg - 0000000,1111111,2222222,etc. should be invalid. But on the other hand if I enter 11111112 then this should be valid as it contains another digit as well. The length of the regex should be between 7 to 15.

I tried with this (?!(\d)\1{6})([0-9]{7,15}) but the same is not working as expected. If there is any better way, please suggest me the same.

I knew someone whose phone number had the same digit repeated throughout. — Mark Cilia Vincenti, Jan 10 '23 at 06:26

blhsing · Accepted Answer · 2023-01-10T05:56:24.893

2

You can use a positive lookahead pattern at the beginning to assert that there exists at least a digit whose following digit isn't the same:

^(?=.*(\d)(?=\d)(?!\1))\d{7,15}$

Demo: https://regex101.com/r/tn9kJd/1

edited Jan 10 '23 at 05:56

answered Jan 10 '23 at 05:23

blhsing

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score 2 · Answer 2 · answered Jan 10 '23 at 08:49

You could use a single negative lookahead to rule out the same digits 0-9 as in C# using \d could match more digits than only 0-9:

^(?!([0-9])\1+$)[0-9]{7,15}$

The pattern matches:

^ Start of string
(?! Negative lookahead, assert that to the right is not
- ([0-9])\1+$ Capture a digit 0-9 in group 1 and repeat that same digit using a backreference \1 one more times till the end of the string
) Close the lookahead
[0-9]{7,15} Match 7-15 digits in the range 0-9
$ End of string

See a regex101 demo.

I need a regex to invalidate all the same digits in a phone number

2 Answers2