regex - JavaScript Regular Expressions Special Characters -

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why regular expression

/^[^-_]*([a-za-z0-9]{3,})+[-_]?[^-_]*$/i

match on string?

,abc,,.

it says string should contain of

  1. minimum 3 letters
  2. followed optional - or _
  3. sequence of number 1 , 2 can repeated infinite times
  4. no - or _ @ beginning or end of string

the regex should not allow other characters a-z, 0-9 , - or _, yet, allows them.

thanks in advance

erm, actually, says:

  • from start,
  • any number of characters not - or _ (matches ,)
  • catastrophically backtrack find @ least 3 alphanumerics (matches abc)
  • optionally match - or _ (matches nothing)
  • any number of characters not - or _ (matches ,,.)
  • to end.

did mean:

/^[a-z0-9]{3,}(?:[-_][12]+)?$/i

correction, misunderstood "point 3".

/^[a-z0-9]{3,}(?:[-_][a-z0-9]{3,})*$/i

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