Typing Error Objects

In TypeScript catch clauses, errors are implicitly typed as unknown (under useUnknownInCatchVariables). You must narrow errors before accessing properties like error.message.

1. Introduction & Architecture

2. Deep Dive & Core Concepts

Because any JavaScript expression can be thrown (throw "string" or throw 404), TypeScript forces catch block variables to be unknown for runtime safety.

3. Basic Code Example

4. Advanced Production Patterns

5. Interactive Code Playground

function parseJSON(input: string) {
  try {
    return JSON.parse(input);
  } catch (err: unknown) {
    if (err instanceof SyntaxError) {
      console.log("JSON Syntax Error:", err.message);
    }
  }
}
parseJSON("{ bad json }");

6. Common Pitfalls & Edge Cases

7. Interview Q&A & Quizzes

Q: Why are catch variables in TypeScript typed as unknown rather than Error?

A: In JavaScript, anything (strings, numbers, objects) can be thrown via throw, so the type cannot be statically guaranteed to be an Error instance.

8. Summary Comparison Table