Mapped Types Development Tutorials, Guides & Insights

Generics allow you to define a placeholder type that will be replaced with a specific type when the function or class is used.

function identity<T>(arg: T): T {
  return arg;
}

const num = identity<number>(42); // T is replaced with number
const str = identity<string>('Hello'); // T is replaced with string

function printId(id: number | string) {
  console.log('ID:', id);
}

printId(101);
printId('ABC123');

type Direction = 'up' | 'down' | 'left' | 'right';

function move(direction: Direction) {
  console.log('Moving', direction);
}

move('up'); // valid
move('right'); // valid
// move('forward'); // error