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JavaScript error

SyntaxError

The JavaScript exception "invalid regular expression flag" occurs when the flags in a regular expression contain any flag that is not one of: d, g, i, m, s, u, v, or y. It may also be raised if the expression contains more than one instance of a valid flag, or when the u and v flags are used together.

Reference entryJavaScriptFetched
This is a reference entry from MDN Web Docs. A full explanation with fixes has not been written yet.

The error messages

SyntaxError: Invalid flags supplied to RegExp constructor 'x' (V8-based)
As listed by MDN Web Docs
SyntaxError: Invalid regular expression flags (V8-based)
As listed by MDN Web Docs
SyntaxError: invalid regular expression flag x (Firefox)
As listed by MDN Web Docs
SyntaxError: Invalid flags supplied to RegExp constructor. (Safari)
As listed by MDN Web Docs
SyntaxError: Invalid regular expression: invalid flags (Safari)
As listed by MDN Web Docs

Details

Category
SyntaxError
Severity
error
Runtime
both

Related errors

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Source: MDN Web Docs. Data fetched 2026-09-25T01:48:37.273Z.