What built-in Error types should you know, and when do you create custom errors?

Short Interview Answer

Know `Error`, `TypeError`, `ReferenceError`, `RangeError`, `SyntaxError`; create custom subclasses for domain-specific failures with stable codes.

Detailed Explanation

Built-ins communicate programmer mistakes vs invalid values. Custom errors (`class ValidationError extends Error`) enable `instanceof` checks and structured fields (`code`, `details`). Set `name` and use `super(message)`; in older targets, fix prototype chain. Prefer error causes (`{ cause }`) to wrap lower-level failures without losing stacks. Don't over-hierarchize — a few meaningful types beat dozens.

Example

class HttpError extends Error {
  constructor(status, message) {
    super(message);
    this.name = 'HttpError';
    this.status = status;
  }
}

Interview Tip

Show a small custom Error class.

Common Mistake

Throwing strings instead of Error objects (loses stack).