Template Literal Types Development Tutorials, Guides & Insights

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

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

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

type Readonly<T> = {
  readonly [K in keyof T]: T[K];
};

interface Car {
  make: string;
  model: string;
  year: number;
}

const myCar: Readonly<Car> = {
  make: 'Toyota',
  model: 'Corolla',
  year: 2020
};

// myCar.make = 'Honda'; // error