Module pattern in TypeScript; having classes doesn't mean you have to use them at all times

car-module.ts

// Run this on the playground by copy-pasting: https://www.typescriptlang.org/play

interface Vehicle {
    brand: string;
    drive(miles: number): void;
    getMileage(): void;
}

interface IsPassengerCarrier {
    carryingCapacity: number;
}

// marker interface
interface PublicTransportVehicle extends Vehicle, IsPassengerCarrier {}

function Car(brand:string): Vehicle{
    const _brand = brand;
    let milesDriven = 0;

    return {
        brand,
        drive(miles) {
            milesDriven += miles;
        },
        getMileage() {
            return milesDriven;
        }
    }
}


function Bus(brand:string, carryingCapacity:number): PublicTransportVehicle {
    const _car = Car(brand);

    return { ..._car, carryingCapacity};
}

const dodge = Car("Dodge Ram");
const doubleDecker = Bus("East Lancashire Coachbuilders‎", 100);
const vehicles = [dodge, doubleDecker];

dodge.drive(50);
dodge.drive(50);
doubleDecker.drive(300)

let output = "";
for (let vehicle of vehicles) {
    output += (`${vehicle.brand} has a mileage of ${vehicle.getMileage()}\n`);
}
alert(output);

Runnable: https://repl.it/@fatso83/Module-Pattern-in-TypeScript