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JS
JavaScript error

SyntaxError

The JavaScript exception "Unexpected '#' used outside of class body" occurs when a hash ("#") is encountered in an unexpected context, most notably outside of a class declaration. Hashes are valid at the beginning of a file as a hashbang comment, or inside of a class as part of a private field.

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

The error message

SyntaxError: Unexpected '#' used outside of class body.
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.