Exploring Postcodes.io Public API Docs with JavaScript

APIs have become the backbone of web and mobile applications as they provide seamless communication between different technology platforms. Postcodes.io is one such public API that provides you with postcode data for the UK. In this blog, we will explore the Postcodes.io public API docs with JavaScript and see how to use different APIs provided by the platform.

Getting Started

To start using the Postcodes.io API, you need to generate an API key. You can do this by signing up for an account on the website. Once you have the API key, we can start exploring the different APIs.

The Postcodes.io APIs are RESTful, which means that they use standard HTTP verbs to query data. The APIs return JSON data, which can be easily parsed using JavaScript.

Example APIs

Lookup API

The Lookup API provides postcode data for a given postcode. To use this API, you need to make an HTTP GET request to the following URL, replacing the POSTCODE value with the postcode you want to look up.

https://api.postcodes.io/postcodes/POSTCODE

Here is an example JavaScript code that uses the Lookup API to get the latitude and longitude of a postcode:

const postcode = 'SE1 2RT';

fetch(`https://api.postcodes.io/postcodes/${postcode}`)
    .then((response) => response.json())
    .then((data) =>
        console.log(
            `Latitude: ${data.result.latitude}, Longitude: ${data.result.longitude}`
        )
    )
    .catch((error) => console.log(error));

Nearest API

The Nearest API provides data for the nearest postcodes to a given latitude and longitude. To use this API, you need to make an HTTP GET request to the following URL, replacing the LATITUDE and LONGITUDE values with the coordinates you want to look up.

https://api.postcodes.io/postcodes?lon=LONGITUDE&lat=LATITUDE

Here is an example JavaScript code that uses the Nearest API to get the nearest postcode to a given latitude and longitude:

const latitude = '51.5045';
const longitude = '-0.0784';

fetch(`https://api.postcodes.io/postcodes?lon=${longitude}&lat=${latitude}`)
    .then((response) => response.json())
    .then((data) => console.log(`Nearest postcode: ${data.result[0].postcode}`))
    .catch((error) => console.log(error));

Bulk Lookup API

The Bulk Lookup API provides postcode data for multiple postcodes in a single request. To use this API, you need to make an HTTP POST request to the following URL with a JSON payload containing an array of postcodes.

https://api.postcodes.io/postcodes

Here is an example JavaScript code that uses the Bulk Lookup API to get the latitude and longitude of multiple postcodes:

const postcodes = ['SE1 2RT', 'W1D 3QU', 'EC2A 4BX'];

fetch('https://api.postcodes.io/postcodes', {
    method: 'POST',
    body: JSON.stringify({ postcodes }),
    headers: { 'Content-Type': 'application/json' },
})
    .then((response) => response.json())
    .then((data) => {
        data.result.forEach((postcode) => {
            console.log(
                `Postcode: ${postcode.query} - Latitude: ${postcode.result.latitude}, Longitude: ${postcode.result.longitude}`
            );
        });
    })
    .catch((error) => console.log(error));

Conclusion

Postcodes.io is a powerful API platform that provides postcode data for the UK. In this blog, we explored some of the main APIs provided by the platform and learned how to use them with JavaScript. There are many more APIs on the platform that you can explore and use to enhance your web or mobile applications.