getPasswordStrength

1/**
2 * Evaluates the strength of a password on a scale from 0 to 4.
3 *
4 * @param password - The password string to evaluate.
5 * @returns A strength index:
6 *  0 - Very weak (common pattern or too short)
7 *  1 - Weak
8 *  2 - Medium
9 *  3 - Strong
10 *  4 - Very strong
11 */
12export function getPasswordStrength(password: string): number {
13  if (!password || password.length < 6) return 0;
14
15  const blacklist = [
16    '1234', 'qwerty', 'password', '1111', 'abc123', 'letmein',
17    'welcome', 'admin', 'root', '0000', 'qazwsx'
18  ];
19
20  const normalized = password.toLowerCase();
21
22  for (const pattern of blacklist) {
23    if (normalized.includes(pattern)) return 0;
24  }
25
26  const lower = /[a-z]/.test(password);
27  const upper = /[A-Z]/.test(password);
28  const digit = /\d/.test(password);
29  const special = /[^a-zA-Z0-9]/.test(password);
30
31  let strength = 0;
32  if (lower) strength += 1;
33  if (upper) strength += 1;
34  if (digit) strength += 1;
35  if (special) strength += 1;
36
37  return strength;
38}

1test('returns 0 for common patterns', () => {
2  expect(getPasswordStrength('123456')).toBe(0);
3  expect(getPasswordStrength('qwerty')).toBe(0);
4  expect(getPasswordStrength('admin123')).toBe(0);
5});
6
7test('returns 1 for lowercase only', () => {
8  expect(getPasswordStrength('abcdef')).toBe(1);
9});
10
11test('returns 2 for lowercase and digits', () => {
12  expect(getPasswordStrength('abc123')).toBe(0); // common pattern
13  expect(getPasswordStrength('abz478')).toBe(2);
14});
15
16test('returns 3 for lowercase, digits and uppercase', () => {
17  expect(getPasswordStrength('Abc123')).toBe(3);
18});
19
20test('returns 4 for all categories', () => {
21  expect(getPasswordStrength('Abc$123')).toBe(4);
22});
23
24test('returns 0 for too short passwords', () => {
25  expect(getPasswordStrength('aB1')).toBe(0);
26});
27
28test('returns 2 for digits and special characters', () => {
29  expect(getPasswordStrength('1234$%')).toBe(2);
30});