iDevMeet

TypeScript · module 18 of 21

Strict Type Safety & Error Modeling

Use strict mode, unknown, never, discriminated results, exhaustive checks, and safe error boundaries.

Course map
string | nullif (value)elsestring.length is allowed herenullhandle the empty caseThe check you would write anyway is what tells the compiler which case it is in. That is why strictmode finds real bugs — it refuses the branch where you forgot the empty case existed.
Strict Type Safety & Error Modeling — the idea in one picture

What this module covers

5 steps · TypeScript

  1. Step 1. Lesson: Strict Type Safety & Error Modeling

    Use strict mode, unknown, never, discriminated results, exhaustive checks, and safe error boundaries. Learning objectives - Recognize when strict type safety & error modeling is the right tool. - Explain the role of unknown, never, Result. - Build a small working example before combining it with a larger interface. - Identify one accessibility, maintainability, or error-handling improvement. Read the example, predict what it will do, then complete the small change described in the check question.

    Use strict mode, unknown, never, discriminated results, exhaustive checks, and safe error boundaries. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [TypeScript] Use the example to demonstrate strict type safety & error modeling.

  2. Step 2. Quiz: Strict Type Safety & Error Modeling

    Check your understanding of Strict Type Safety & Error Modeling.

    unknown prevents unsafe operations until runtime evidence narrows the value. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [TypeScript] Complete the knowledge check.

  3. Step 3. Exercise: Strict Type Safety & Error Modeling

    Replace unsafe any-based error handling with unknown, narrowing, and a typed Result union.

    This exercise turns the Strict Type Safety & Error Modeling lesson into a working code change. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [TypeScript] Does the solution use unknown and never and Result?

  4. Step 4. Review lab: Explain & improve Strict Type Safety & Error Modeling

    Rebuild the exercise without copying the solution. Then improve it in two ways: make the code easier to understand and add one useful edge case, responsive behavior, accessibility improvement, or error state. Finally, write a short explanation of how unknown, never, Result work together.

    Rebuilding from memory and improving an edge case turns recognition into durable skill. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [TypeScript] Does the improved version still use unknown, never, Result clearly?

  5. Step 5. Mini project: Strict Type Safety & Error Modeling

    Build a typed validation pipeline that reports every success and failure state exhaustively.

    The mini project combines the module lesson, quiz, and exercise into one portfolio-ready result. In TypeScript, make the state/interaction visible in the UI so completion is easy to verify.

    Check yourself: [TypeScript] Does the project apply the module's strict type safety & error modeling skills?

Loading code lab...