10-tip-calculator.js

1/**
2 * 🍽️ TipEasy - Restaurant Tip Calculator
3 *
4 * You're building TipEasy, an app that helps diners calculate the right
5 * tip based on how they'd rate their dining experience. No more awkward
6 * mental math at the table!
7 *
8 * Service Rating → Tip Percentage:
9 *   - 1 (terrible)  → 5%
10 *   - 2 (poor)      → 10%
11 *   - 3 (okay)      → 15%
12 *   - 4 (good)      → 20%
13 *   - 5 (excellent) → 25%
14 *
15 * Return an object with:
16 *   - tipPercentage: the percentage as a number (e.g., 15)
17 *   - tipAmount: the calculated tip rounded to 2 decimal places
18 *   - totalAmount: bill + tip rounded to 2 decimal places
19 *
20 * Rules:
21 *   - If billAmount is 0 or negative, return null
22 *   - If serviceRating is not an integer from 1 to 5, return null
23 *
24 * Example:
25 *   calculateTip(50, 4)
26 *   → { tipPercentage: 20, tipAmount: 10.00, totalAmount: 60.00 }
27 *
28 * @param {number} billAmount - The bill amount in dollars
29 * @param {number} serviceRating - Service rating from 1 to 5
30 * @returns {{ tipPercentage: number, tipAmount: number, totalAmount: number } | null}
31 */
32export function calculateTip(billAmount, serviceRating) {
33  if(billAmount <= 0){
34    return null
35  }
36
37  if (!Number.isInteger(serviceRating) || serviceRating < 1 || serviceRating > 5) {
38    return null;
39  }
40  
41  function getTipPercentage(serviceRating){
42    switch(serviceRating){
43      case 1:
44        return 5;
45      case 2:
46        return 10;
47      case 3:
48        return 15;
49      case 4:
50        return 20;
51      default:
52        return 25;
53    }
54  }
55    
56  function getTipAmount(tipPercentage, billAmount){
57    return Number(((tipPercentage/100)*billAmount).toFixed(2))
58  }
59
60  let tipPercentage = getTipPercentage(serviceRating)
61  let tipAmount = getTipAmount(tipPercentage, billAmount)
62  let totalAmount = Number((tipAmount + billAmount).toFixed(2))
63
64  return {tipPercentage, tipAmount, totalAmount}
65
66}
67