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@lokal-id/core

Indonesian data primitives for apps and AI agents: NIK, NPWP, phone numbers, Rupiah, terbilang, holidays and working days, Kemendagri regions with postal codes, and Samaran, which masks Indonesian personal data before it reaches an LLM and restores it afterwards.

No dependencies. Part of Lokal · Bahasa Indonesia

Install

npm install @lokal-id/core

For Python backends there is a port with identical results: pip install lokal-id (docs).

Usage

import { parseNik, parsePhone, formatRupiah, parseRupiah, terbilang, addWorkingDays, Samaran } from '@lokal-id/core';
import { listWilayah, searchWilayah, wilayahName, findByPostalCode, parseAlamat } from '@lokal-id/core/wilayah';

parseNik('3201011508950001', { lookupWilayah: wilayahName });
// { valid: true, province: 'Jawa Barat', regency: 'Kabupaten Bogor', gender: 'L', birthDate: '1995-08-15', … }
parsePhone('0812 3456 7890');           // { e164: '+6281234567890', operator: 'Telkomsel', … }
formatRupiah(1500000);                  // 'Rp1.500.000'
parseRupiah('sejuta setengah');         // { amount: 1500000, approximate: false }
terbilang(1500000, { currency: true }); // 'satu juta lima ratus ribu rupiah'
addWorkingDays('2026-03-17', 1);        // '2026-03-25', skipping Nyepi and Lebaran
listWilayah('32.76');                   // districts of Kota Depok
findByPostalCode('16431');              // villages that use this postal code
parseAlamat('Kebayoran Baru, Jaksel').kecamatan?.code; // '31.74.07'

Samaran

const samaran = new Samaran();
const { text } = samaran.mask('nama saya budi santoso, NIK 3201011508950001, HP 0812-3456-7890');
// 'nama saya [NAME_1], NIK [NIK_1], HP [PHONE_1]'

samaran.unmask(await llm(text));        // placeholders are replaced with the original values

The same value always gets the same placeholder, so the model can still deduplicate and join. Use mode: 'partial' for logs and admin screens (3201********0001).

With the Vercel AI SDK, wrap the model and every call is masked and restored, streaming and tool calls included:

import { wrapLanguageModel } from 'ai';
import { samaranMiddleware } from '@lokal-id/core/ai-sdk';

const model = wrapLanguageModel({ model: openai('gpt-5'), middleware: samaranMiddleware() });

@lokal-id/core/wilayah loads about 4.4 MB of region data and runs on Node only. The main entry point does not load it and is safe for browsers.

Data

Data	Source
Regions: 38 provinces, 416 regencies, 98 cities, 7,285 districts, 8,496 kelurahan, 75,266 villages	cahyadsn/wilayah (MIT), following Kepmendagri 300.2.2-2138/2025
Postal codes for all 83,762 villages	cahyadsn/wilayah_kodepos (MIT)
Holidays and cuti bersama for 2026 and 2027	SKB 3 Menteri. Other years return an error, not a guess

Detection limits and full documentation are in the Lokal README.

License

MIT