Node.js script for querying city districts for a list of geo coordinates using Nominatim API

nominatim-reverse-geocode.js

const fs = require('fs');
const request = require('request');

const customHeaderRequest = request.defaults({
    headers: { 'User-Agent': 'Reverse geocode search' }
});

let output = '';

// expected input format in input_data.csv
// is a list of latitude and longitude pairs, for example:
//
// 52.520856,13.413779
// 52.420140,13.492070
// ...

fs.readFile('input_data.csv', (err, data) => {
    if (err) throw err;
    const array = data.toString().split('\n');
    const lonLats = array.map(item => item.split(','));
    const urls = lonLats.map(
        item =>
            `https://nominatim.openstreetmap.org/reverse?format=jsonv2&lat=${item[0]}&lon=${item[1]}`
    );

    sendRequest(urls);
});

function sendRequest(urls) {
    setTimeout(() => {
        const url = urls[0];
        customHeaderRequest(url, (err, response, body) => {
            console.log(`request: ${url}`);
            if (err) throw err;
            if (!err && response.statusCode === 200) {
                const data = JSON.parse(body);
                const district =
                    data.address.city_district || data.address.town;
                output += `${district}\n`;

                urls.shift();
                if (urls.length === 0) return writeOutput();
                sendRequest(urls);
            }
        });
    }, 1500);
}

function writeOutput() {
    fs.writeFile('output_data.csv', output, err => {
        if (err) throw err;
        console.log('File written!');
    });
}