TypeScript in depth

The type system as a design tool. Inference, narrowing, generics, and the errors that mean the model is wrong — not a catalog of utility types. A type that lies (any, assertion, optional everywhere), then the type that would have caught the bug at compile time.

What you will learn

  • Structural typing, freshness, and excess properties
  • Narrowing, discriminants, and never
  • Generics, inference, and when to write the param
  • Utility types, mapped types, and template literals
  • Declaration files, modules, and the compiler API you feel
  • What belongs in the type vs the runtime check

How it works

A type that lies (any, assertion, optional everywhere), then the type that would have caught the bug at compile time.

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