SyntaxError: unlabeled break must be inside loop or switch

The JavaScript exception "unlabeled break must be inside loop or switch" occurs when a break statement is not inside a loop or a switch statement.

Message

SyntaxError: Illegal break statement (V8-based) SyntaxError: unlabeled break must be inside loop or switch (Firefox) SyntaxError: 'break' is only valid inside a switch or loop statement. (Safari)

Error type

SyntaxError.

What went wrong?

break statements can be used to exit a loop or a switch statement, and using them elsewhere is a syntax error. Alternatively, you can provide a label to the break statement to break out of any statement with that label — however, if the label does not reference a containing statement, another error SyntaxError: label not found will be thrown.

Examples

Unsyntactic break

break cannot be used outside switch or loops.

js
let score = 0; function increment() { if (score === 100) break; // SyntaxError: unlabeled break must be inside loop or switch } score++; }

Maybe instead of break, you intend to use return to early-terminate a function.

js
let score = 0; function increment() { if (score === 100) { return; } score++; }

Using break in callbacks

break cannot be used in callbacks, even if the callback is called from a loop.

js
let containingIndex = 0; const matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], ]; while (containingIndex < matrix.length) { matrix[containingIndex].forEach((value) => { if (value === 5) { break; // SyntaxError: unlabeled break must be inside loop or switch } }); containingIndex++; }

Instead, refactor the code so the break is used outside the callback.

js
let containingIndex = 0; const matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], ]; outer: while (containingIndex < matrix.length) { for (const value of matrix[containingIndex]) { if (value === 5) { break outer; } } containingIndex++; }
js
let containingIndex = 0; const matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9], ]; while (containingIndex < matrix.length) { if (matrix[containingIndex].includes(5)) { break; } containingIndex++; }

There's no way to early-terminate a forEach() loop. You can use some() instead, or convert it to a for...of loop.

js
array.forEach((value) => { if (value === 5) { break; // SyntaxError: unlabeled break must be inside loop or switch } // do something with value });
js
array.some((value) => { if (value === 5) { return true; } // do something with value return false; });
js
for (const value of array) { if (value === 5) { break; } // do something with value }

See also