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Magic numbers and hidden constants

TSjunior

Практика →

There's a stub auth validation function on main. A colleague sent a PR with the full implementation: token length, attempt limit, TTL, user lockout. The logic works, but the code is peppered with magic numbers and strings with no context. Walk the diff — how many of these should be lifted into constants?

PR: lesson.typescript +10 −06 проблем

11 export function validateAuthToken(token: string, attempts: number): boolean {

2- // TODO: implement

3- return token.length > 0

2+ if (token.length < 32) return false

3+ if (attempts > 5) return false

5+ const now = Date.now()

6+ const expiry = parseInt(token.slice(0, 13), 10)

7+ if (now - expiry > 3600000) return false

9+ if (token.startsWith('dev_') && process.env.NODE_ENV === 'production') {

10+ return false

11+ }

12+

13+ return true

414 }

515

616 export function lockUser(userId: string): void {

7- // TODO: implement

8- db.users.update(userId, { status: 1 })

17+ const lockUntil = Date.now() + 900000

18+ db.users.update(userId, { lockedUntil: lockUntil, status: 2 })

919 }

Шаг 1 из 8

What is a "magic value"?

A magic value is any number or string in code without a name or explanation. Examples: `< 32`, `* 3600000`, `status === 2`, `role === 'admin'`. Problems: (1) unclear what it means; (2) duplication — the same number in multiple places; (3) changing it forces you to update everywhere and not miss any. Look at the code — how many such values do you see?