Module 5: TypeScript

MODULE 05 · 2 LESSONS

Add useful static guarantees at application boundaries without replacing runtime validation.

Project checkpoint: Convert the tracker data layer to strict TypeScript.

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Module 5 learning loopA four-step visual showing type inference, unions, narrowing, strict mode.Module 5 learning loop1Type Inference2Unions3Narrowing4Strict Mode

Module 5 learning loop

  1. 1Type Inference
  2. 2Unions
  3. 3Narrowing
  4. 4Strict Mode
Module 5 learning loop: a practical sequence used in this lesson.

What this module changes in your work

  • Model known states and narrow unknown values before use.
  • Keep compile-time types honest by validating network and storage data at runtime.
  • Use type inference, unions, narrowing in one coherent implementation.
  • Complete this evidence-backed checkpoint: Convert the tracker data layer to strict TypeScript.

Lessons

PROJECT CHECKPOINT

Turn typescript into evidence

Convert the tracker data layer to strict TypeScript.

  • Write acceptance criteria for type inference before implementation.
  • Keep the change small enough that a reviewer can connect it to the intended behavior.
  • Use the most direct check available for unions and save the result.
  • Record one decision you would keep and one you would revisit after feedback.

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