Javascript Regex to avoid same character twice consecutively

Question

I need a regular expression to avoid having the same character(@ is the character) twice consecutively but can have them at muliple places. For example:

someword@someword is ok
someword@@someword is not ok
someword@someword@someword is ok too.

So basically this is my existing regular expression /^([a-zA-Z0-9'\-\x80-\xff\*\+ ]+),([a-zA-Z0-9'\-\x80-\xff\*\+\@ ]+)$/ where the first group is the last name and second group is the first name. I have introduced a magical character @ in the first name group which I will replace with a space when saving. The problem is I cannot have consecutive @ symbols.

and what have you tried??

Psych Half
– Psych Half

2013-11-06 13:01:13 +00:00
Commented Nov 6, 2013 at 13:01 — Psych Half
– Psych Half, Commented Nov 6, 2013 at 13:01

Reeno · Accepted Answer · 2013-11-06 13:25:53Z

6

Looks for any repeated characters (repeated once):

/(.)\1/.test(string) // returns true if repeated characters are found

Looks for a repeated @:

string.indexOf('@@') !== -1 // returns true if @@ is found

edited Nov 6, 2013 at 13:25

answered Nov 6, 2013 at 13:04

Reeno

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2 Comments

Bryan Oakley Over a year ago

This matches any repeated character. I think the question is specifically about the @ character. You might want to address that in your answer.

Vineeth Bolisetty Over a year ago

@Reeno sorry about that. I just wanted to explain more.

TWL · Accepted Answer · 2013-11-06 13:11:37Z

3

str.replace(/(@{2,})/g,'@')

works for any number of occorences.. @@, @@@, @@@@ etc

answered Nov 6, 2013 at 13:11

TWL

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1 Comment

Vineeth Bolisetty Over a year ago

replace looks fine too. I can even look for consecutive @s at the back end too. But I wanted it in the regex as I have a particular set of characters allowed.

Nzall · Accepted Answer · 2013-11-06 13:03:06Z

2

str.replace(/@@/g,'@')

finds and replaces all instances of '@@' by '@'. Also works if you have more than 2 consecutive '@' signs. Doesn't replace single @ signs or things that aren't @ signs.

edit: if you don't have to replace but just want to test on it:

/@@/.test(str)

answered Nov 6, 2013 at 13:03

Nzall

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Comments

Rajdeep Singh · Accepted Answer · 2013-11-06 13:24:36Z

1

Try this regex

/^(?!.*(.)\1)[a-zA-Z][a-zA-Z\d@]*$/

This regex will not allow @ consecutively

edited Nov 6, 2013 at 13:24

answered Nov 6, 2013 at 13:06

Rajdeep Singh

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3 Comments

Bryan Oakley Over a year ago

This matches any repeated character. I think the question is specifically about the @ character. You might want to address that in your answer.

Rajdeep Singh Over a year ago

made the changes, have a look

Nasta Over a year ago

@RajdeepSingh I tried again, it still doesn't allow any successive characters

Nasta · Accepted Answer · 2022-07-25 13:59:25Z

0

I didn't find any pure regex solution that worked for your use-case

So here is mine:

^([a-z0-9]@?)*[a-z0-9]$
 |____________|______|
       |          |-> Makes sure your string ends with an alphanumeric character
       |-> Makes sure the start of the string is a mix of single @ or alphanumeric characters
       |   It has to start with an alphanumeric character

answered Jul 25, 2022 at 13:59

Nasta

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