Js Regular expression for first name

Question

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?

Answer 1

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.