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3.0.1 • Public • Published

Ideal Postcodes Javascript Client

JavaScript (browser) client for api.ideal-postcodes.co.uk

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@ideal-postcodes/core-browser is the JavaScript browser client for api.ideal-postcodes.co.uk

Our JavaScript client implements a common interface defined at @ideal-postcodes/core-interface.

High level client documentation can be found at core-interface.

In depth client documentation can be found at core-interface.ideal-postcodes.dev.

Tested against a suite of modern and legacy, mobile and desktop browsers.

@ideal-postcodes/core-browsershould be consumed by a bundler or transpiler (e.g. webpack, parcel, rollup) for minification, module resolution and specific browser support.

core-browser-bundled provides pre-bundled versions of core-browser, which can be immediately dropped into a page.


Example Setup

Webpack Status

Parcel Status

Rollup Status

Polymer Status

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Configuration & Usage


npm install @ideal-postcodes/core-browser


import { Client } from "@ideal-postcodes/core-browser";

const client = new Client({ api_key: "iddqd" });

Configuration options


const addresses = await lookupPostcode({ client: client, postcode: "SW1A2AA" });

Catch Errors

import { errors } from "@ideal-postcodes/core-browser";
const { IdpcRequestFailedError } = errors;

try {
  await lookupAddress({ client, query: "10 downing street" });
} catch (error) {
  if (error instanceof IdpcRequestFailedError) {
    // IdpcRequestFailedError indicates a 402 response code
    // Possibly the key balance has been depleted

HTTP Agent and legacy browser support

core-browser uses the Fetch API under the hood to facilitate HTTP requests.

A configuration object can be passed to the Client constructor as a second argument to override certain attributes on the Request of all subsequent fetch requests. Request configuration is documented here.

If you need to support older browsers, please include a fetch polyfill and transpile this library down to ES3. Alternatively use one of our pre-transpiled outputs at ideal-postcodes/core-browser-bundled.


The client exposes a number of simple methods to get at the most common tasks when interacting with the API. Below is a (incomplete) list of commonly used methods.

For a complete list of client methods, including low level resource methods, please see the core-interface documentation

Lookup a Postcode

Return addresses associated with a given postcode

const postcode = "id11qd";

const addresses = await lookupPostcode({ client, postcode });

Method options

Search for an Address

Return addresses associated with a given query

const query = "10 downing street sw1a";

const addresses = await lookupAddress({ client, query });

Method options

Search for an Address by UDPRN

Return address for a given udprn

Invalid UDPRN will return null

const udprn = 23747771;

const address = await lookupUdprn({ client, udprn });

Method options


npm test



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npm i @ideal-postcodes/core-browser

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