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46.1 - Parcel Delivery Calculator, practice (JS lessons — arguments and return)

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📘 Task: Parcel Delivery Calculator

Create the "Parcel Delivery Calculator" app.

The user enters the parcel weight in kg and the delivery distance in km, and also marks whether express delivery is needed. After clicking the button, the final delivery cost needs to be calculated.

🧩 Main condition: architecture of 4 functions

• 3 calculator functions — each is responsible for its own part of the calculation (weight, distance, urgency).
• 1 main function — doesn't calculate anything directly itself. It calls all three calculator functions inside itself, passes them the needed arguments, and uses what they returned.

💰 Rates (hardcoded as constants):

• 📦 Base fee — 15 $
• ⚖️ Price per 1 kg of weight — 3 $
• 📏 Price per 1 km of distance — 2 $
• 🚀 Express delivery surcharge — +25% of the final amount

📐 Functions you need to write:

• Function 1 — weight:
  calculateWeightCost(). Inside the function itself get the weight and store it in the variable weightKg, then return weightKg * 3
• Function 2 — distance:
  calculateDistanceCost() — takes no arguments. Inside the function itself get the distance and store it in the variable distanceKm, then return distanceKm * 2
• Function 3 — urgency:
  calculateUrgentSurcharge(amount) — takes the amount. Inside the function itself, create a flag variable isUrgent (true/false, set manually). If isUrgent === true — returns amount * 1.25, otherwise — returns amount unchanged.
• Function 4 — main:
  calculateTotalCost() — all the other functions are called inside it. The final result needs to be displayed on the screen.
• Print the answer in this format:
  "Total cost: 50 $"

🧪 Example:

Given:

• ⚖️ Weight — 5 kg
• 📏 Distance — 10 km
• 🚀 Express — no

Calculation (step by step):

• calculateWeightCost() → 5 * 3 = 15 $
• calculateDistanceCost() → 10 * 2 = 20 $
• 15 (base) + 15 + 20 = 50 $
• calculateUrgentSurcharge(50) → isUrgent = false → stays 50 $

Total cost: 50 $