Practice: Exception Handling

Which keyword starts a block where code that might throw an error is placed?

• Finally

• Catch

• Throw

• Try

Answer explanation

The try block wraps risky code so any error it throws can be caught. Catch handles the error after try exits.

Tags

Blooms Level: Remember

When a developer uses `throw new Error('msg')`, what does the catch block parameter contain?

• A boolean flag value

• A numeric status code

• An Error object instance

• A raw stack trace string

Answer explanation

When an Error object is explicitly thrown, the catch parameter holds that Error object, giving access to properties like message and name. A stack trace string is just one property of the object, not the parameter itself.

Tags

Blooms Level: Remember

A developer needs cleanup code to run after a try block, even if catch also runs. Where does it go?

• In a throw statement

• In the try block

• In the finally block

• In the catch block

Answer explanation

Finally executes after try and catch complete, making it the right place for cleanup like closing files or resetting UI state.

Tags

Blooms Level: Apply

Which keyword raises a custom error from inside a function?

• Catch

• Error

• Raise

• Throw

Answer explanation

Throw signals an error and stops normal execution. Error is the constructor used with throw, not the keyword that raises it.

Tags

Blooms Level: Remember

Which TWO statements about try-catch-finally are correct? (Select all that apply)

• Try must be paired with catch, finally, or both

• Throw can only appear inside a catch block

• Catch only runs when an error is thrown

• Errors thrown in try skip remaining try statements

• Finally runs only when no error occurs

Answer explanation

Catch fires only on errors, and try requires at least one of catch or finally. Finally runs in both cases, and throw is allowed anywhere.

Tags

Blooms Level: Analyze

A function divides two numbers and may receive a string argument. Where should the conversion attempt be wrapped?

• Inside a try block

• Inside a throw statement

• Inside a finally block

• Inside a catch block

Answer explanation

Code that might fail belongs in try so any thrown error can be caught. Catch handles the failure after it occurs, not before.

Tags

Blooms Level: Apply

What happens to code after a throw statement in the same try block?

• It runs only if catch is absent

• It runs normally afterward

• It is skipped entirely

• It runs after finally completes

Answer explanation

Throw immediately exits the current block, so later statements in try are skipped. Control jumps to the matching catch block.

Tags

Blooms Level: Understand

Which try-catch-finally structure is syntactically valid in JavaScript?

• Try followed only by finally

• Try with no catch or finally

• Finally without a try block

• Catch without a try block

Answer explanation

Try requires catch, finally, or both to be valid. A standalone try or a catch/finally without try causes a syntax error.

Tags

Blooms Level: Remember

Which TWO scenarios are appropriate uses of throw? (Select all that apply)

• Ending a normal loop iteration

• Logging a debug message to console

• Signaling invalid function arguments

• Returning a value from a function

• Rejecting input that fails validation

Answer explanation

Throw is for exceptional conditions like bad arguments or failed validation. Logs use console methods, loops use break or continue, and values use return.

Tags

Blooms Level: Apply

Why use try-catch instead of letting errors propagate uncaught?

• It removes the need for unit testing

• It hides bugs from developers

• It prevents the script from crashing

• It speeds up code execution

Answer explanation

Catching errors lets the program continue or fail gracefully instead of crashing. It does not improve speed and should not be used to silence real bugs.

Tags

Blooms Level: Understand