Lesson overview · Free interview practice

Generics

Master generic types and constraints.

Topics in the full lesson
  • Introduction to Generics
  • Generic Functions
  • Generic Classes
  • Using Constraints with extends
  • Keyof Constraint
  • Generic Interfaces
  • Generic Constraints and Interfaces
  • Best Practices
  • Exercises

Practice Problems

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TheoryEasy

Generics: Type Parameters and Why They Exist

Question

What is a generic type in TypeScript? Show the canonical identity example and explain why generics beat any for reuse.

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Generics vs `any`: Preserving Type Information

Question

When you have a function that "works with any type," why prefer a generic over any? Show the difference in inferred return types.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Generic Constraints with `extends`

Question

What is a generic constraint, and why do you need one? Show a generic function that accesses properties of its parameter — with and without a constraint.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Generic Classes

Question

How do you define a generic class? Show the canonical container example (Stack<T>) and explain how constraints flow to methods.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

`keyof` and Indexed Access Types

Question

What does the keyof operator do, and what is an indexed access type? Show how they combine with generics to make property access type-safe.

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Explain your reasoning or try an implementation before comparing answers.

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