javascript - Js Regular expression for first name - Stack Overflow

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I am looking for a regular expression which fulfil below conditions

• Min 1 and Max 50 char
• No spaces at the beginning and ending of string
• Allow only one space, dot between 2 words.

I am using below expression which causes catastrophic backtracking issue. Expression -

/^[a-zA-Z]+(?:(?:|['_\. ])([a-zA-Z]*(\.\s)?[a-zA-Z])+)*$/

How can I prevent this issue?

I am looking for a regular expression which fulfil below conditions

• Min 1 and Max 50 char
• No spaces at the beginning and ending of string
• Allow only one space, dot between 2 words.

I am using below expression which causes catastrophic backtracking issue. Expression -

/^[a-zA-Z]+(?:(?:|['_\. ])([a-zA-Z]*(\.\s)?[a-zA-Z])+)*$/

How can I prevent this issue?

• javascript
• regex
• formvalidation.io

Share Improve this question Follow edited Oct 10, 2017 at 10:16 Rashmi Narware asked Oct 10, 2017 at 10:11 Rashmi NarwareRashmi Narware 4111 silver badge55 bronze badges 4

• 1 Try /^(?=.{1,50}$)[a-z]+(?:['_.\s][a-z]+)*$/i. – Wiktor Stribiżew Commented Oct 10, 2017 at 10:14
• I updated my question, underscore will be there in pattern – Rashmi Narware Commented Oct 10, 2017 at 10:17
• It would be good to have a set of test strings. Try them at regex101./r/TmJTBD/3 – Wiktor Stribiżew Commented Oct 10, 2017 at 10:18
• /^(?=.{1,50}$)[a-z]+(?:['_.\s][a-z]+)*$/i. This worked for me . Thanks you so much. – Rashmi Narware Commented Oct 10, 2017 at 10:55

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1 Answer 1

Sorted by: Reset to default 9

You may use

/^(?=.{1,50}$)[a-z]+(?:['_.\s][a-z]+)*$/i

See the regex demo.

Details

• ^ - start of string
• (?=.{1,50}$) - there must be 1 to 50 chars in the string
• [a-z]+ - 1 or more ASCII letters
• (?:['_.\s][a-z]+)* - 0 or more sequences of
  • ['_.\s] - a ', _, . or whitespace
  • [a-z]+ - 1 or more ASCII letters
• $ - end of string
• /i - a case insensitive modifier.

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