Throwing errors in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the throw statement do in JavaScript?

The throw statement stops normal execution and creates an error. It sends a value (usually an Error object) that can be caught by try...catch blocks.

beginner

How do you create a custom error message when throwing an error?

You create a new Error object with a message, like throw new Error('My message'). This message helps explain what went wrong.

beginner

What happens if you throw an error outside of a try...catch block?

The program stops running and shows the error message in the console or environment. This is called an uncaught error.

intermediate

Can you throw any type of value in JavaScript?

Yes, you can throw any value like strings, numbers, or objects. But it is best practice to throw Error objects for better debugging.

beginner

Why is it useful to throw errors in your code?

Throwing errors helps you catch problems early, stop wrong actions, and give clear messages about what went wrong. It makes your code safer and easier to fix.

What keyword is used to create an error intentionally in JavaScript?

A error

B catch

C try

D throw

The throw keyword is used to create an error intentionally.

Which of these is the best way to throw a custom error message?

A throw new Error('Error happened');

B throw 'Error happened';

C throw Error;

D throw error('Error happened');

Using throw new Error('message') creates a proper Error object with a message.

What happens if an error is thrown but not caught?

A The program stops and shows the error.

B The error is ignored.

C The program continues silently.

D The error is logged but program continues.

An uncaught error stops the program and shows the error message.

Can you throw a number as an error in JavaScript?

A No, only Error objects can be thrown.

B Yes, any value can be thrown.

C Only strings can be thrown.

D Only objects can be thrown.

JavaScript allows throwing any value, but Error objects are recommended.

Why should you throw errors in your code?

A To hide problems from users.

B To avoid using try...catch.

C To stop wrong actions and explain problems.

D To make code run faster.

Throwing errors helps stop wrong actions and gives clear messages about problems.

Explain how the throw statement works and why it is useful.

Think about what happens when something goes wrong in your code.

Describe the difference between throwing a string and throwing an Error object.

Consider what makes debugging easier.