interface Car {
make: string;
model: string;
mileage?: number;
}
let myCar: Required<Car> = {
make: 'Ford',
model: 'Focus',
mileage: 12000 // `Required` forces mileage to be defined
};
console.log(myCar);
{ make: 'Ford', model: 'Focus', mileage: 12000 }