JavaScript Fundamentals · Error Handling · Lesson 31 of 48
Throwing Your Own Errors
Concept
Throwing Your Own Errors
The throw keyword lets your own functions signal that something went wrong, using the built-in Error object or a custom message.
Throwing immediately stops the current function, unwinding up the call stack until a matching catch block handles it — or, if none exists, crashing the program.
- Explain the core idea behind Throwing Your Own Errors.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Throwing Your Own Errors. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Write a function divide(a, b) that throws an Error when b is 0, then call it inside a try/catch.
Ask about this lesson or your next move. The guide explains the path without taking the work away from you.
Ready for the next lesson?
Mark this lesson complete when you have finished the exercise.
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