kenteken-kit

formatKentekenPartial formats live input as a Dutch plate while the user types.

Tiny Dutch kenteken formatting, parsing, and validation for JavaScript and TypeScript.

This package is intentionally small:

• no runtime dependencies
• pure functions, no class instance state
• modern ESM build
• TypeScript declarations
• partial formatting for live inputs and OCR cleanup
• parse results with issue codes instead of only true or false

Install

npm install kenteken-kit

Usage

import {
  formatKenteken,
  formatKentekenPartial,
  isKenteken,
  normalizeKenteken,
  parseKenteken,
} from "kenteken-kit";

normalizeKenteken(" kjr-50.s "); // "KJR50S"
formatKenteken("kjr50s"); // "KJR-50-S"
formatKentekenPartial("kjr5"); // "KJR-5"
isKenteken("G-001-BB"); // true

parseKenteken("G-001-BB");
// {
//   input: "G-001-BB",
//   normalized: "G001BB",
//   formatted: "G-001-BB",
//   series: 10,
//   seriesPattern: "X-999-XX",
//   isValid: true,
//   issues: []
// }

API

normalizeKenteken(raw)

Uppercases raw and removes every character except ASCII letters and digits.

formatKenteken(raw)

Returns a normalized kenteken with RDW-style dash groups when the value matches one of the supported series. Unknown 6-character shapes are returned normalized.

formatKentekenPartial(raw)

Formats up to six normalized characters for live input fields. When a partial value has a single matching series prefix, it uses that series' grouping. Otherwise it falls back to simple letter/digit runs.

parseKenteken(raw)

Returns normalized text, formatted text, series metadata, and validation issues.

Issue codes:

• too_short
• too_long
• unknown_series
• disallowed_letter
• forbidden_combination

isKenteken(raw)

Convenience boolean around parseKenteken(raw).isValid.

KENTEKEN_SERIES

Metadata for the supported Dutch kenteken series. Each item includes a series number, display pattern, normalized mask, group lengths, and example.

Rules and scope

The formatter supports 14 common Dutch kenteken series. Validation applies general RDW-style letter and combination rules, but this package is not an issuance check. It does not tell you whether a specific kenteken actually exists, belongs to a specific vehicle category, or was issued on a specific date.

For vehicle data, use RDW open data or the official RDW kentekencheck. This package is not affiliated with RDW.

Useful RDW references:

• https://www.rdw.nl/de-kentekenplaat/cijfers-en-letters-op-de-kentekenplaat
• https://www.rdw.nl/de-kentekenplaat/overzicht-van-kentekenseries

License

MIT