SyntaxError: unlabeled break must be inside loop or switch
The JavaScript exception "unlabeled break must be inside loop or switch" occurs when abreak statement is not inside a loop or aswitch 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
What went wrong?
break statements can be used to exit a loop or aswitch statement, and using them elsewhere is a syntax error. Alternatively, you can provide alabel to thebreak statement to break out of any statement with that label — however, if the label does not reference a containing statement, another errorSyntaxError: label not found will be thrown.
Examples
Unsyntactic break
break cannot be used outsideswitch or loops.
let score = 0;function increment() { if (score === 100) break; // SyntaxError: unlabeled break must be inside loop or switch } score++;}Maybe instead ofbreak, you intend to usereturn to early-terminate a function.
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.
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 thebreak is used outside the callback.
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++;}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 aforEach() loop. You can usesome() instead, or convert it to afor...of loop.
array.forEach((value) => { if (value === 5) { break; // SyntaxError: unlabeled break must be inside loop or switch } // do something with value});array.some((value) => { if (value === 5) { return true; } // do something with value return false;});for (const value of array) { if (value === 5) { break; } // do something with value}