JavaScript Error Handling 2

Question 1

What types of errors can be thrown in JavaScript?

Accepted Answer

Any value including strings, numbers, and objects

Answer

JavaScript's `throw` statement can throw any value — strings, numbers, objects, or Error instances. However, best practice is to throw Error objects or subclasses to preserve stack traces.

Question 2

What is the purpose of the `finally` block in try/catch/finally?

Accepted Answer

It always runs regardless of whether an error occurred

Answer

The `finally` block always executes after `try` and any applicable `catch` block, regardless of whether an error occurred or was caught. It's used for cleanup code.

Question 3

What is a RangeError in JavaScript?

Accepted Answer

An error when a value is not within the allowed range

Answer

A `RangeError` is thrown when a value is not within the allowed range. Examples: passing an invalid length to `new Array(-1)`, calling `toFixed()` with a number out of range, or infinite recursion causing a stack overflow.

Question 4

How do you create a custom error type in JavaScript?

Accepted Answer

By extending the `Error` class with `class CustomError extends Error {}`

Answer

You create custom errors by extending the `Error` class. Call `super(message)` in the constructor, and set `this.name` to your custom error name for proper identification.

Question 5

What is the `Error.prototype.stack` property?

Accepted Answer

A string containing the call stack at the time the error was created

Answer

The `stack` property is a string that contains the error message followed by the call stack (list of function calls) at the point where the error was created. It's invaluable for debugging.

JavaScript Practice Test

JavaScript Practice Test

JavaScript Error Handling 2