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Extras are additional services that guests can add to their reservations, such as breakfast, parking, or special check-in/out times. This guide explains how to manage extras and how pricing is recalculated.

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Available Extra Services

The JS Mini Hotel system supports the following extra services:

Breakfast

€10 per dayAdd daily breakfast service for your guests.

Parking

€15 per dayReserved parking space during the stay.

Late Check-out

€30 one-timeCheck out later than standard time.

Early Check-in

€20 one-timeCheck in earlier than standard time.

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Adding Extras to a Reservation

Extras can be added to any existing reservation using the addExtras() function.
1

Prepare the extras array

Each extra is an object with name, price, and quantity properties:
const extras = [
  { name: 'Breakfast', price: 10, quantity: 5 },
  { name: 'Parking', price: 15, quantity: 5 }
]
Quantity typically matches the number of nights for daily services, or is set to 1 for one-time charges.
2

Add extras to the reservation

Use the reservation ID to add extras:
main.js:63-69
const updatedReservation = addExtras(
  hotel,
  'RES-001',
  [
    { name: 'Breakfast', price: 10, quantity: 5 },
    { name: 'Parking', price: 15, quantity: 5 }
  ]
)
3

Verify the updated reservation

The function returns the updated reservation with extras and recalculated price:
console.log('Updated reservation:', updatedReservation)

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How the Function Works

Let’s examine the addExtras() function in detail:
main.js:154-166
function addExtras(hotel, reservationId, extras) {
  if (getReservationById(hotel, reservationId) === undefined) {
    console.log('La reserva no existe, no se pueden añadir extras')
    return
  }
  const [reservation] = hotel.reservations.filter(
    reservation => reservation.id === reservationId
  )
  reservation.extras.push(...extras)
  reservation.totalPrice = updateTotalPriceWithExtras(reservation, extras)

  return reservation
}
  1. Validation: Checks if the reservation exists
  2. Find reservation: Locates the reservation in the hotel’s reservations array
  3. Add extras: Pushes the new extras to the reservation’s extras array
  4. Recalculate price: Updates the total price to include extras
  5. Return: Returns the updated reservation object

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Price Recalculation

When extras are added, the total price is automatically recalculated.

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How Extras Pricing Works

The system calculates the total extras price and adds it to the base room price:
utils.js:114-117
export function updateTotalPriceWithExtras(reservation, extras) {
  const extrasTotalPrice = getExtrasPrice(extras)
  return extrasTotalPrice + reservation.totalPrice
}
utils.js:122-127
export function getExtrasPrice(extras) {
  return extras.reduce((acc, extra) => {
    acc += extra.price * extra.quantity
    return acc
  }, 0)
}
The price calculation formula is: totalPrice = roomPrice + (extra.price × extra.quantity) for each extra.

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Example Scenarios

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Scenario 1: Adding Daily Services

A 5-night stay with breakfast and parking: 
// Original reservation: 5 nights × €150/night = €750
const reservation = createReservation(
  hotel,
  301,
  {
    name: 'Ana García',
    email: '[email protected]',
    phone: '+34 612345678',
    dni: '12345678A'
  },
  '2026-04-10',
  '2026-04-15'
)

// Add breakfast and parking for all 5 nights
const withExtras = addExtras(
  hotel,
  reservation.id,
  [
    { name: 'Breakfast', price: 10, quantity: 5 },
    { name: 'Parking', price: 15, quantity: 5 }
  ]
)

​
Scenario 2: One-Time Charges

Adding early check-in and late check-out: 
// Add one-time charges
const withSpecialTimes = addExtras(
  hotel,
  reservation.id,
  [
    { name: 'Early Check-in', price: 20, quantity: 1 },
    { name: 'Late Check-out', price: 30, quantity: 1 }
  ]
)

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Scenario 3: Mixed Services

Combining daily and one-time services: 
const fullExtras = addExtras(
  hotel,
  reservation.id,
  [
    { name: 'Breakfast', price: 10, quantity: 5 },
    { name: 'Late Check-out', price: 30, quantity: 1 }
  ]
)

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Error Handling

If you try to add extras to a non-existent reservation, the function will log an error and return undefined:
addExtras(hotel, 'RES-INVALID', [...])
// Console: "La reserva no existe, no se pueden añadir extras"

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Best Practices

For daily services like breakfast or parking, set the quantity equal to the number of nights:
const nights = reservation.nights
const extras = [
  { name: 'Breakfast', price: 10, quantity: nights },
  { name: 'Parking', price: 15, quantity: nights }
]
Always verify the reservation exists before attempting to add extras:
const reservation = getReservationById(hotel, reservationId)
if (reservation) {
  addExtras(hotel, reservationId, extras)
}
Maintain consistent pricing across your application by referencing a constants file:
const EXTRA_PRICES = {
  BREAKFAST: 10,
  PARKING: 15,
  LATE_CHECKOUT: 30,
  EARLY_CHECKIN: 20
}

const extras = [
  { name: 'Breakfast', price: EXTRA_PRICES.BREAKFAST, quantity: 5 }
]

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Viewing Extras in Invoices

When a guest checks out, extras are itemized in the invoice:
utils.js:160-181
export function createInvoice(hotel, reservation) {
  const room = getRoomByNumber(hotel, reservation.roomNumber)

  return {
    reservationId: reservation.id,
    guest: reservation.guest,
    room: {
      number: room.number,
      type: room.type
    },
    checkIn: reservation.checkIn,
    checkOut: reservation.checkOut,
    price: {
      room: getTotalPrice(room, reservation.checkIn, reservation.checkOut),
      extras: getExtrasPrice(reservation.extras),
      total:
        getTotalPrice(room, reservation.checkIn, reservation.checkOut) +
        getExtrasPrice(reservation.extras)
    },
    emisionDate: Temporal.Now.plainDateISO()
  }
}
The invoice separately shows room charges and extras charges for transparency.

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Next Steps

Creating Reservations

Learn how to create reservations from scratch

Generating Reports

View revenue reports that include extras income

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