Question 168552 in Javascript Question posted in
A very good W3school tutorial can be found here.

Can someone give a regex expression for the condition in React JS?

Spaces

  • Will only be allowed within the alpha text
  • Multiple spaces will be allowed within the field but cannot be consecutive

Dashes

  • Will only be allowed within the alpha text (boyd-lawson" or "boyd – lawson" is ok, but "boyd-" and "boyd " and " "-boyd" is not)
  • Multiple dashes will be allowed within the field but cannot be consecutive

Periods

  • Cannot be the first character in the field
  • Multiple periods will be allowed within the field but cannot be consecutive

Apostrophes

  • Multiple apostrophes will be allowed within the field but cannot be consecutive

I tried using the below expression
/^(?!.*(?:ss|-{2,}|.{2,}|'{2,}))(?=[A-Za-zs.-']+$)(?!.*(?:^.))/g

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2

Answers


  1. 0

    Can you try this

    const pattern = /^(?!.*--)(?!.*..)(?!.*[^ws]s+)(?!.*s[^ws])(?!.*.s)(?!.*s.)(?!.*'s)(?!.*s')(?!.*[^ws-]s+)(?!.*s[^ws-])(?!.*-s)(?!.*s-)[A-Za-z0-9s.-]*[A-Za-z0-9]$/;
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  2. 0

    Here is a regular expression which attempts to refactor your requirements into one single definition.

    • The first character cannot be dash, space, or period.
    • Within the text, a character can be any non-dash, non-space, non-period, non-apostrophe character, or a dash, space, period, or apostrophe if it is not immediately followed by another.
    • The last character cannot be dash, space, period, or apostrophe.

    To permit a single-character field, the expression after the first character is optional.

    We separately have to prohibit two adjacent apostrophes at the beginning or end using lookarounds.

    /^(?!'')[^- .](([^- .']|[- .'][^- .'])*[^- .])?(?<!'')$/

    You might want to restrict [^- .] and [^- .'] further if you specifically require these characters to be strictly alphanumeric. For example, the above formulation will permit two adjacent commas or circumflexes; maybe you want to require actual text, or add some other further constraints.

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