Prototypes

// Constructor function
function Vehicle(type) {
    this.type = type;
}

// Add method to prototype
Vehicle.prototype.describe = function() {
    return `This is a ${this.type}`;
};

Vehicle.prototype.wheels = 4;

const car = new Vehicle("car");
const bike = new Vehicle("bike");
bike.wheels = 2;  // Override for this instance

console.log(car.describe());
console.log(`Car wheels: ${car.wheels}`);
console.log(bike.describe());
console.log(`Bike wheels: ${bike.wheels}`);

// Check prototype chain
console.log(car.hasOwnProperty('type')); // true
console.log(car.hasOwnProperty('describe')); // false (on prototype)