Advanced Types Development Tutorials, Guides & Insights

Here, input can be either a string or a number, and the function handles each case accordingly.

Mapped types allow you to create new types by transforming existing ones. This is especially useful for applying the same transformation to each property in a type.

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