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Fix regex invalid escape

Invalid escape sequences in a regular expression cause a syntax error. Not all characters can be escaped, and some need escaping.

Common causes

  • Escaping a character that doesn't need it.
  • Invalid escape sequence (e.g. \k in JavaScript).
  • Unescaped special character in a character class.

How to fix

  • Check the regex flavor documentation for valid escapes.
  • Escape only . * + ? [ ] ( ) { } | ^ $ \ as needed.
  • Test with Regex Tester.

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