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← All coursesTypeScript: What the Type System Checks6 levels · 27 lessons

Reading the type system~7 min
Literal types & widening~6 min
The satisfies operator~6 min
Structural typing & excess property checks~8 min
Type Foundations · Review~5 min

any, unknown, and the assertion escape hatch~7 min
Type guards~6 min
Discriminated unions~7 min
Exhaustiveness & never~6 min
any, unknown & Narrowing · Review~5 min

Generics that earn the brackets~7 min
Where inference comes from~7 min
Utility types~7 min
Generics · Review~5 min

Template literal types~7 min
Conditional types~7 min
Mapped types & key remapping~7 min
The infer keyword~7 min
Type Transformation · Review~5 min

What survives to runtime~7 min
Type-only imports & emit~7 min
Module resolution~7 min
Modules & Emit · Review~5 min

Declaration files~7 min
Declaration merging~6 min
Compiler configuration~7 min
Declarations & The Compiler · Review~5 min

Course

TypeScript: What the Type System Checks

The TypeScript features you use every day: satisfies, generics, inference and emit.

Start free: Reading the type system