05-library-card.js

1/**
2 * 📚 Maple Town Library
3 *
4 * The librarian at Maple Town Public Library is tired of manually checking
5 * whether members can borrow books. She asks you to automate it!
6 *
7 * A member can borrow books ONLY if ALL of these are true:
8 *   1. They are at least 6 years old
9 *   2. They have a valid library card (hasValidCard is true)
10 *   3. They have zero overdue books
11 *
12 * Return an object with two properties:
13 *   - allowed: boolean (true if they can borrow, false otherwise)
14 *   - message: string (a descriptive message)
15 *
16 * Check conditions in this order and return the FIRST failure:
17 *   - Age < 6:
18 *     { allowed: false, message: "Too young - must be at least 6 years old" }
19 *
20 *   - No valid card:
21 *     { allowed: false, message: "Invalid library card - please renew at the front desk" }
22 *
23 *   - Has overdue books:
24 *     { allowed: false, message: "Please return your X overdue book(s) first" }
25 *     (replace X with the actual number of overdue books)
26 *
27 *   - All conditions met:
28 *     { allowed: true, message: "You may borrow up to 3 books" }
29 *
30 * @param {number} memberAge - The member's age
31 * @param {boolean} hasValidCard - Whether they have a valid library card
32 * @param {number} overdueBooks - Number of overdue books
33 * @returns {{ allowed: boolean, message: string }}
34 */
35export function canBorrowBook(memberAge, hasValidCard, overdueBooks) {
36  if(memberAge < 6){
37    return  { allowed: false, message: "Too young - must be at least 6 years old" }
38  } else if(!hasValidCard){
39    return { allowed: false, message: "Invalid library card - please renew at the front desk" }
40  } else if(overdueBooks){
41    return { allowed: false, message: `Please return your ${overdueBooks} overdue book(s) first` }
42  }else {
43    return { allowed: true, message: "You may borrow up to 3 books" }
44  }
45}
46