phone-purchase.ts

/*
You Don't Know JS: Up & Going
Chapter 1: Into Programming - PRACTICE
https://github.com/getify/You-Dont-Know-JS/blob/master/up%20%26%20going/ch1.md
*/

let accountBalance = 303.91;
let totalPriceOfPurchase = 0;

const TAX_RATE = 0.08;
const PHONE_PRICE = priceWithTax(99.99);
const ACCESSORY_PRICE = priceWithTax(9.99);
const SPENDING_THRESHOLD = 50;

export function buy(): string {
  let phoneCounter = 0;
  let accessoryCounter = 0;

  while (totalPriceOfPurchase < accountBalance) {
    accountBalance -= PHONE_PRICE;
    totalPriceOfPurchase += PHONE_PRICE;
    phoneCounter++;

    if (accountBalance > SPENDING_THRESHOLD) {
      accountBalance -= ACCESSORY_PRICE;
      totalPriceOfPurchase += ACCESSORY_PRICE;
      accessoryCounter++;
    }
  }

  return formatPrice(
    totalPriceOfPurchase,
    phoneCounter,
    accessoryCounter,
  );
}

function priceWithTax(price: number): number {
  return price + (price * TAX_RATE);
}

function formatPrice(
  price: number,
  phoneCount: number,
  accessoryCount: number,
): string {

  return `You've spent $ ${price.toFixed(2)} on ${phoneCount} phones and ${accessoryCount} accessories`;
}