SyntaxError: functions cannot be labelled

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

The error messages

SyntaxError: In non-strict mode code, functions can only be declared at top level, inside a block, or as the body of an if statement. (V8-based)

As listed by MDN Web Docs

SyntaxError: In strict mode code, functions can only be declared at top level or inside a block. (V8-based)

As listed by MDN Web Docs

SyntaxError: Generators can only be declared at the top level or inside a block. (V8-based)

As listed by MDN Web Docs

SyntaxError: Async functions can only be declared at the top level or inside a block. (V8-based)

As listed by MDN Web Docs

SyntaxError: functions can only be labelled inside blocks (Firefox)

As listed by MDN Web Docs

SyntaxError: functions cannot be labelled (Firefox)

As listed by MDN Web Docs

SyntaxError: generator functions cannot be labelled (Firefox)

As listed by MDN Web Docs

SyntaxError: async function declarations can't appear in single-statement context (Firefox)

As listed by MDN Web Docs

SyntaxError: Unexpected keyword 'function'. Function declarations are only allowed inside block statements or at the top level of a program. (Safari)

As listed by MDN Web Docs

SyntaxError: Function declarations are only allowed inside blocks or switch statements in strict mode. (Safari)

As listed by MDN Web Docs

SyntaxError: Unexpected token '*'. Cannot use generator function declaration in single-statement context. (Safari)

As listed by MDN Web Docs

SyntaxError: Unexpected keyword 'function'. Cannot use async function declaration in single-statement context. (Safari)

As listed by MDN Web Docs

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