Challenge 2: Generics

Solve a task using generics and constraints.

Generics challenge

In this challenge you will solve tasks that combine generic functions and constraints. You learned to define type parameters with <T>, add constraints with extends, and use keys with keyof. Generics preserve type safety while allowing code to work with any type.

Exercise uzunluk generic function

Define a generic function named uzunluk: <T extends { length: number }>(x: T): number. Its body should be return x.length. Print the result of calling uzunluk("merhaba") with console.log.

Show example solution

function uzunluk<T extends { length: number }>(x: T): number {
  return x.length;
}
console.log(uzunluk("merhaba"));

Exercise Field access with keyof

Define a generic function named al: <T, K extends keyof T>(obj: T, anahtar: K): T[K]. Its body should be return obj[anahtar]. The kisi object is { ad: "Ayşe", yas: 30 }. Print the result of calling al(kisi, "ad") with console.log.

Show example solution

function al<T, K extends keyof T>(obj: T, anahtar: K): T[K] {
  return obj[anahtar];
}
const kisi = { ad: "Ayşe", yas: 30 };
console.log(al(kisi, "ad"));

Test yourself

What is used to require a generic type parameter to have a specific structure?
- readonly
- implements
- abstract
- extends constraint
Show answer

extends constraint — The extends constraint requires the type parameter to have a specific structure or type; for example <T extends { length: number }>.

extends constraint

function uzunluk<T ____ { length: number }>(x: T): number {
  return x.length;
}

Show answer

function uzunluk<T extends { length: number }>(x: T): number {
  return x.length;
}

Generic concepts

<T>

Type parameter
extends

Constraint
keyof

Key set
default

Default type

Next lesson: Challenge 3: Type systems

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