Jump target cannot cross function boundary in TypeScript

Jump target cannot cross function boundary in TypeScript #

The "Jump target cannot cross function boundary" error occurs when we try to use a break statement outside of a for loop, e.g. in forEach() or a function. To solve the error only use a break statement in for loops and exit forEach() functions by throwing and catching an error.

Here are two examples of how the error occurs.

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const arr = ['a', 'b', 'c'];

arr.forEach((value) => {
  if (value === 'b') {
    // ⛔️ Error: Jump target cannot cross function boundary.ts(1107)
    break;
  }
  console.log(value);
});

function example() {
  // ⛔️ Error: Jump target cannot cross function boundary.ts(1107)
  break; // 👉️ use return (not break)
}

The break statement is used to terminate the current loop.

To solve the error if using the forEach method, throw an error in a try/catch block to break out of the loop if you're in a function and can't use the break statement.

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const arr = ['a', 'b', 'c'];

const BreakError = {};

try {
  arr.forEach((element) => {
    if (element === 'b') {
      throw BreakError;
    }
    console.log(element); // 👉️ a
  });
} catch (err) {
  if (err !== BreakError) throw err;
}

In the code snippet, we throw an error to break out of the iteration. We can't use the break keyword inside a function, so we wrap the function in a try/catch block and throw an error to exit when we need to.

We can use the break statement in the following scenarios:

• basic for loops
• for ... of loops
• for ... in loops
• while loops
• switch statements

If you're using a forEach loop and trying to use a break statement, you can try using a for ... of loop instead. You can use the break keyword in a for ... of loop.

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const arr = ['a', 'b', 'c'];

for (const element of arr) {
  if (element === 'b') {
    break;
  }
  console.log(element); // 👉️ a
}

The error often occurs when we try to use a break statement to exit a function.

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function example() {
  // ⛔️ Error: Jump target cannot cross function boundary.ts(1107)
  break; // 👉️ use return (not break)
}

You can use the return statement to exit a function.

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function example() {
  return;
}

Conclusion #

The "Jump target cannot cross function boundary" error occurs when we try to use a break statement outside of a for loop, e.g. in forEach() or a function. To solve the error only use a break statement in for loops and exit forEach() functions by throwing and catching an error.