09-password-strength.js

1/**
2 * 🔒 SecureApp Password Checker
3 *
4 * You're building the signup page for SecureApp, a new productivity tool.
5 * The product manager wants a password strength meter that gives users
6 * real-time feedback as they type their password.
7 *
8 * The checker evaluates 5 criteria:
9 *   1. At least 8 characters long
10 *   2. Contains at least one uppercase letter (A-Z)
11 *   3. Contains at least one lowercase letter (a-z)
12 *   4. Contains at least one number (0-9)
13 *   5. Contains at least one special character (!@#$%^&*()_+-=[]{}|;:,.<>?) 
14 *
15 * Strength levels based on how many criteria are met:
16 *   - 0–1 criteria → "weak"
17 *   - 2–3 criteria → "medium"
18 *   - 4 criteria   → "strong"
19 *   - All 5        → "very strong"
20 *
21 * Rules:
22 *   - Empty string → "weak"
23 *   - Non-string input → "weak"
24 *
25 * @param {string} password - The password to evaluate
26 * @returns {string} "weak", "medium", "strong", or "very strong"
27 */
28export function checkPasswordStrength(password) {
29
30  function hasUpperCase(pass) {
31    return /[A-Z]/.test(pass);
32  }
33
34  function hasLowerCase(pass) {
35    return /[a-z]/.test(pass);
36  }
37
38  function hasNumber(pass){
39     return /\d/.test(pass)
40  }
41
42  function hasSpecialChar(pass){
43     return /[!@#$%^&*()_+\-=\[\]{}|;:,.<>?]/.test(pass);
44  }
45
46  if(typeof password !== "string") {
47   return "weak"
48  }
49  password = password.trim()
50
51   if(password === ""){
52    return "weak"
53   }
54
55   let criteriaNum = 0;
56
57   if(password.length >= 8 ){
58    criteriaNum ++
59   }
60
61   if(hasUpperCase(password)){
62    criteriaNum += 1
63   }
64
65   if(hasLowerCase(password)){
66    criteriaNum += 1
67   }
68
69   if(hasNumber(password)){
70    criteriaNum += 1
71   }
72
73   if(hasSpecialChar(password)){
74    criteriaNum += 1
75   }
76
77   if(criteriaNum === 5){
78    return "very strong"
79   }else if(criteriaNum === 4) {
80    return "strong"
81   } else if (criteriaNum >= 2){
82    return "medium"
83   }else {
84     return "weak"
85   }
86}
87