How do I validate and format Haitian phone numbers (+509)?

Question

My signup form accepts Haitian phone numbers. Users type them in many ways: `3712-3456`, `509 37 12 34 56`, `+50937123456`. How do I validate and store them consistently?

Accepted Answer

Haitian numbers are **8 digits** after the country code **+509**. Normalize everything to **E.164** (`+50937123456`) for storage, and format only for display.

Use **libphonenumber-js**. Numbering plans change over time, and the library tracks them for you:

```ts
import { parsePhoneNumberFromString } from 'libphonenumber-js';

export function normalizeHtPhone(input: string): string | null {
  const p = parsePhoneNumberFromString(input, 'HT'); // default country for numbers typed without +509
  if (!p || !p.isValid()) return null;
  return p.number;            // '+50937123456' (E.164), store this
}

// display: p.formatInternational() → '+509 3712 3456'
```

Tips:
- Default the country to **HT**, but accept international numbers too. Many users are in the diaspora (US, Canada, France, Dominican Republic, Chile…).
- Store E.164 in the database with a unique index if the phone is used for login.
- If you send OTP by SMS, **verify** the number before trusting it, and rate-limit sends: SMS costs money and is a target for abuse.

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