SyntaxError: unlabeled break must be inside loop or switch

The JavaScript exception "unlabeled break must be inside loop or switch" occurs when a {{jsxref("Statements/break", "break")}} statement is not inside a loop or a {{jsxref("Statements/switch", "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#

{{jsxref("SyntaxError")}}.

What went wrong?#

{{jsxref("Statements/break", "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-nolint example-bad 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 {{jsxref("Statements/return", "return")}} to early-terminate a function.

```js example-good
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-nolint example-bad 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 example-good
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 example-good 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 {{jsxref("Array/forEach", "forEach()")}} loop. You can use {{jsxref("Array/some", "some()")}} instead, or convert it to a {{jsxref("Statements/for...of", "for...of")}} loop.

```js-nolint example-bad
array.forEach((value) => {
  if (value === 5) {
    break; // SyntaxError: unlabeled break must be inside loop or switch
  }
  // do something with value
});

```js example-good array.some((value) => { if (value === 5) { return true; } // do something with value return false; });

```js example-good
for (const value of array) {
  if (value === 5) {
    break;
  }
  // do something with value
}

See also#

• {{jsxref("Statements/break", "break")}}