Lesson overview · Free interview practice

Basic Types

Master fundamental TypeScript types and type inference.

Topics in the full lesson
  • Introduction to TypeScript Types
  • Primitive Types
  • Type Annotations
  • Arrays
  • Tuples
  • Type Inference
  • Any, Unknown, and Void Types
  • Type Assertions
  • Best Practices
  • Exercises

Practice Problems

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TheoryEasy

Tuples and `readonly` Tuples

Question

What's the difference between an array and a tuple in TypeScript? Show the readonly and as const variants.

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

The 7 TypeScript Primitive Types

Question

What are the primitive types in TypeScript? Show the type annotation for each.

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TheoryEasy

Literal Types and `as const`

Question

What is a literal type? Why does TypeScript widen const x = "hello" to string, and how does as const change that?

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

`never` and `void`: Commonly Confused

Question

What's the difference between void and never in TypeScript? When does each show up?

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

`any` vs `unknown`: The Always-Prefer-`unknown` Decision

Question

What's the difference between any and unknown in TypeScript? Which should you reach for in practice?

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Explain your reasoning or try an implementation before comparing answers.

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