Sometimes errors do not happen automatically — but you still want to stop the program when something is wrong.
JavaScript allows you to create and throw your own errors using the throw keyword.
Throwing custom errors helps you control program flow and show clear, meaningful messages when invalid data is found.
Why Use Custom Errors
- Validate user input
- Stop execution when rules are broken
- Show meaningful error messages
- Improve debugging
- Make applications safer
Custom errors give developers full control over error handling.
Here, the program checks a condition and throws an error when it is invalid.
This prevents the program from continuing with wrong data.
The error is thrown inside the function and caught safely.
This allows the program to handle the problem instead of crashing.
These examples show how custom errors help control program behavior and improve reliability.
By learning to throw and handle custom errors, students gain the ability to build safer, more predictable, and professional JavaScript applications.