Features

rut.ts is deliberately a focused toolkit: twelve small functions that each do one job well, so you compose only what you need. Every throwing function also has a non-throwing safe mode ({ throwOnError: false }).

The functions#

How they group#

Validation#

• validate() — the acceptance gate (shape + verifier, optional strict mode)
• isValidRut() — type guard that narrows to the branded Rut
• isRutLike() — cheap pre-filter, no verifier math

Formatting & cleaning#

• format() — canonical display shape, with incremental typing mode
• clean() — strip formatting and leading zeros down to digits
• mask() — partially hide a RUT for display (12.***.***-5)

Comparison#

• equals() — answer "same RUT?" across shapes, checking validity by default ({ requireValid: false } for pure shape comparison)

Decomposition#

• decompose() — body + verifier together
• getBody() — body only
• getVerifier() — verifier only

Generation & math#

• generate() — valid random RUTs
• calculateVerifier() — derive the Modulo 11 check digit

Shared behavior#

All functions:

• ✅ Are fully typed — complete TypeScript definitions
• ✅ Bound input length before parsing (ReDoS-safe)
• ✅ Emit generic errors — never echo the offending value
• ✅ Accept multiple shapes — dots, hyphens, or plain digits
• ✅ Handle leading zeros — the lenient helpers (clean, format, equals) strip them; the acceptance predicates (validate, isValidRut, isRutLike) reject them since 5.0.0

See it run#