Finally block in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of finally block with return

What is the output of this JavaScript code?

function test() {
  try {
    return 'try';
  } finally {
    return 'finally';
  }
}
console.log(test());

Javascript

function test() {
  try {
    return 'try';
  } finally {
    return 'finally';
  }
}
console.log(test());

A try

B undefined

C finally

D Error

💡 Hint

Remember that the finally block runs after try and can override return values.

In JavaScript, if both try and finally blocks have return statements, the return in finally overrides the one in try.

❓ Predict Output

intermediate

Finally block execution with thrown error

What will be logged to the console?

try {
  throw new Error('Oops');
} finally {
  console.log('Cleanup');
}

Javascript

try {
  throw new Error('Oops');
} finally {
  console.log('Cleanup');
}

A Cleanup\nError: Oops

B No output

C Error: Oops

D Cleanup

💡 Hint

The finally block runs even if an error is thrown.

The finally block runs and logs 'Cleanup'. The error is thrown but not caught, so it appears as an uncaught error after the log.

❓ Predict Output

advanced

Return value with try, catch, and finally

What is the output of this code?

function example() {
  try {
    throw 'error';
  } catch (e) {
    return 'catch';
  } finally {
    return 'finally';
  }
}
console.log(example());

Javascript

function example() {
  try {
    throw 'error';
  } catch (e) {
    return 'catch';
  } finally {
    return 'finally';
  }
}
console.log(example());

A catch

B finally

C undefined

D error

💡 Hint

Consider which return statement takes priority.

The finally block's return overrides the catch block's return, so 'finally' is returned.

❓ Predict Output

advanced

Finally block with thrown error and catch

What will be the output?

try {
  throw 'fail';
} catch (e) {
  console.log('Caught:', e);
  throw 'new fail';
} finally {
  console.log('Finally block');
}

Javascript

try {
  throw 'fail';
} catch (e) {
  console.log('Caught:', e);
  throw 'new fail';
} finally {
  console.log('Finally block');
}

A Finally block

B Finally block\nCaught: fail

C Caught: fail

D Caught: fail\nFinally block

💡 Hint

The finally block runs after catch, even if catch throws again.

The catch block logs 'Caught: fail' and throws a new error. The finally block runs and logs 'Finally block'.

🧠 Conceptual

expert

Effect of finally on thrown error propagation

Consider this code:

function f() {
  try {
    throw 'error';
  } finally {
    return 'finally';
  }
}

try {
  console.log(f());
} catch (e) {
  console.log('Caught:', e);
}

What will be printed to the console?

A finally

B Error: error

C undefined

D Caught: error

💡 Hint

A return in finally overrides thrown errors.

The throw in try is overridden by the return in finally, so no error propagates and 'finally' is printed.