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JavaScript regular expression has nothing to repeat

SyntaxError: nothing to repeat

JavaScript rejected the regular expression because a repetition operator like *, +, or ? does not follow a valid token.

SyntaxError: nothing to repeatregex

Observed message

SyntaxError: nothing to repeat

Why it happens

  • A quantifier appears at the start of a pattern or after an invalid token.
  • A grouping or escape sequence is malformed around the quantifier.
  • The regular expression was assembled dynamically and produced invalid syntax.

How to fix it

  1. Check the token immediately before the quantifier and make sure it is repeatable.
  2. Wrap the intended fragment in a group if the quantifier should apply to multiple characters.
  3. Log dynamically built regex patterns before constructing RegExp objects.

Official reference

MDN: SyntaxError: nothing to repeat

Related errors

SyntaxError: invalid regular expression flagJavaScript regular expression used an invalid flagReferenceError: can't access lexical declaration before initializationJavaScript accessed a let or const binding before initializationReferenceError: assignment to undeclared variableJavaScript assigned to an undeclared variableTypeError: BigInt value can't be serialized in JSONJavaScript BigInt value cannot be serialized in JSON

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JavaScript regex nothing to repeat: causes and fixes | Error Atlas