vendingModule.js

module.exports = {
  create: function () {
    var display = [
      { name: "chips", price: 0.75, quantity: 5 },
      { name: "soda", price: 1.50, quantity: 0 },
      { name: "candy", price: 1.00, quantity: 5 }
    ];

    var vendingMachine = {
      "restock": function (itemIndex) {
        var selectedItem = display[itemIndex];
        // Validations
        if (!selectedItem) {
          return "Invalid selected item";
        }
        selectedItem.quantity = 5;
        return selectedItem.name + " was restocked";
      },
      "purchase": function (paymentAmount, itemIndex) {
        var selectedItem = display[itemIndex];

        // Validations
        if (!selectedItem) {
          return "Invalid selected item";
        }
        if (selectedItem.price > paymentAmount) {
          return "Insufficient funds";
        }
        if (selectedItem.quantity <= 0) {
          return "Out of stock";
        }

        // Calculate change owed
        var changeOwed = paymentAmount - selectedItem.price;

        // Dispense product
        selectedItem.quantity--;
        return "Dispensed " + selectedItem.name + ". Change owed: " + changeOwed;
      }
    };

    return vendingMachine;
  }
};