JavaScript and TypeScript library for Nigeria's National Digital Alphanumeric Postcode System (NDAPS), the building-level postcode NIPOST launched in October 2026. Parse, validate and format postcodes offline, and call the postcode.gov.ng API for lookup, autocomplete and reverse geocoding.

Part of the ng-postcode project, which has the same behaviour in Rust and Python and an MCP server for AI assistants. All three run the same shared test cases.

npm install ng-postcode-js

No runtime dependencies. Needs Node 20 or later, or any runtime with fetch.

Offline

Expected failures are returned as values, so the type checker makes you handle them.

import { Postcode, parse } from "ng-postcode-js";

const code = parse("ek 01 a03 fk 01");
if (code instanceof Postcode) {
  console.log(String(code)); // EK-01-A03-FK-01
  console.log(code.compact); // EK01A03FK01, store this
  console.log(code.spaced); // EK 01 A03 FK 01
  console.log(code.prefix("area")); // EK-01-A03-FK
} else {
  console.log(String(code)); // e.g. "invalid lga segment"
}

parse accepts hyphenated, spaced or compact input in either case.
parseLenient first swaps look-alikes that cannot occur where they stand (O/0, I/1, S/5, B/8) and reports how many it changed.
fromSegments assembles a code from its parts and zero-fills the LGA and unit.
isValid answers yes or no.

A well-formed code is not necessarily assigned to a building. Only the API can confirm that a postcode exists.

API

import { Postcode, parse } from "ng-postcode-js";
import { ApiError, lookup } from "ng-postcode-js/api";
import { Client, TransportError } from "ng-postcode-js/client";

const code = parse("FC-03-B06-AG-12");
if (!(code instanceof Postcode)) throw new Error(String(code));

const client = new Client(process.env.NG_POSTCODE_API_KEY ?? "");
const found = await client.send(lookup(code, 1));

if (found instanceof ApiError || found instanceof TransportError) {
  console.error(String(found)); // e.g. "invalid_api_key (401): ..."
} else {
  console.log(found.valid, found.status); // true valid
}

ng-postcode-js/api covers lookup, autocomplete, reverse and nearby. Each returns a plain Request, and decode turns a status and body into a typed result, so it works with any HTTP client. A request that cannot succeed, such as a level outside 1 to 5, an empty autocomplete or a coordinate that is not finite, throws RangeError before anything is sent.

The client refuses redirects, so the key is never sent to another host. Response fields keep the API's own names, such as administrative_address.

Get a key from the NIPOST developer dashboard. Level 1 lookups confirm a code is assigned; levels 2 and up return address details and consume credits.