customers.json

{"latitude": "52.986375", "user_id": 12, "name": "Christina McArdle", "longitude": "-6.043701"}
{"latitude": "51.92893", "user_id": 1, "name": "Alice Cahill", "longitude": "-10.27699"}
{"latitude": "51.8856167", "user_id": 2, "name": "Ian McArdle", "longitude": "-10.4240951"}
{"latitude": "52.3191841", "user_id": 3, "name": "Jack Enright", "longitude": "-8.5072391"}
{"latitude": "53.807778", "user_id": 28, "name": "Charlie Halligan", "longitude": "-7.714444"}
{"latitude": "53.4692815", "user_id": 7, "name": "Frank Kehoe", "longitude": "-9.436036"}
{"latitude": "54.0894797", "user_id": 8, "name": "Eoin Ahearn", "longitude": "-6.18671"}
{"latitude": "53.038056", "user_id": 26, "name": "Stephen McArdle", "longitude": "-7.653889"}
{"latitude": "54.1225", "user_id": 27, "name": "Enid Gallagher", "longitude": "-8.143333"}
{"latitude": "53.1229599", "user_id": 6, "name": "Theresa Enright", "longitude": "-6.2705202"}
{"latitude": "52.2559432", "user_id": 9, "name": "Jack Dempsey", "longitude": "-7.1048927"}
{"latitude": "52.240382", "user_id": 10, "name": "Georgina Gallagher", "longitude": "-6.972413"}
{"latitude": "53.2451022", "user_id": 4, "name": "Ian Kehoe", "longitude": "-6.238335"}
{"latitude": "53.1302756", "user_id": 5, "name": "Nora Dempsey", "longitude": "-6.2397222"}
{"latitude": "53.008769", "user_id": 11, "name": "Richard Finnegan", "longitude": "-6.1056711"}
{"latitude": "53.1489345", "user_id": 31, "name": "Alan Behan", "longitude": "-6.8422408"}
{"latitude": "53", "user_id": 13, "name": "Olive Ahearn", "longitude": "-7"}
{"latitude": "51.999447", "user_id": 14, "name": "Helen Cahill", "longitude": "-9.742744"}
{"latitude": "52.966", "user_id": 15, "name": "Michael Ahearn", "longitude": "-6.463"}
{"latitude": "52.366037", "user_id": 16, "name": "Ian Larkin", "longitude": "-8.179118"}
{"latitude": "54.180238", "user_id": 17, "name": "Patricia Cahill", "longitude": "-5.920898"}
{"latitude": "53.0033946", "user_id": 39, "name": "Lisa Ahearn", "longitude": "-6.3877505"}
{"latitude": "52.228056", "user_id": 18, "name": "Bob Larkin", "longitude": "-7.915833"}
{"latitude": "54.133333", "user_id": 24, "name": "Rose Enright", "longitude": "-6.433333"}
{"latitude": "55.033", "user_id": 19, "name": "Enid Cahill", "longitude": "-8.112"}
{"latitude": "53.521111", "user_id": 20, "name": "Enid Enright", "longitude": "-9.831111"}
{"latitude": "51.802", "user_id": 21, "name": "David Ahearn", "longitude": "-9.442"}
{"latitude": "54.374208", "user_id": 22, "name": "Charlie McArdle", "longitude": "-8.371639"}
{"latitude": "53.74452", "user_id": 29, "name": "Oliver Ahearn", "longitude": "-7.11167"}
{"latitude": "53.761389", "user_id": 30, "name": "Nick Enright", "longitude": "-7.2875"}
{"latitude": "54.080556", "user_id": 23, "name": "Eoin Gallagher", "longitude": "-6.361944"}
{"latitude": "52.833502", "user_id": 25, "name": "David Behan", "longitude": "-8.522366"}

distanceCalculator.js

#!/usr/local/bin/node

/**
 * Head office coordinates (Dublin, Ireland)
 * @type {GpsPoint}
 */
var headOffice = new GpsPoint(53.3381985, -6.2592576);

/**
 * Maximum distance from the head office (in kilometers)
 * @type {Number}
 */
var maximumDistance = 100;

/**
 * Gps point object
 * @param latitude
 * @param longitude
 * @constructor
 */
function GpsPoint(latitude, longitude) {

    /**
     * Point object
     * @param coordinate
     * @constructor
     */
    function Point(coordinate) {

        /**
         * Returns radians
         * @returns {Number}
         */
        this.toRadians = function () {
            return coordinate * Math.PI / 180;
        };

        /**
         * Returns original value
         * @returns {String}
         */
        this.getCoordinate = function () {
            return coordinate;
        };

        /**
         * Override: toString
         * @returns {String}
         */
        this.toString = function () {
            return this.getCoordinate();
        };
    }

    // Convert latitude and longitude to Point objects
    latitude = new Point(latitude);
    longitude = new Point(longitude);

    /**
     * Getter: latitude
     * @returns {GpsPoint.Point}
     */
    this.getLatitude = function () {
        return latitude;
    };

    /**
     * Getter: longitude
     * @returns {GpsPoint.Point}
     */
    this.getLongitude = function () {
        return longitude;
    };
}

/**
 * Returns the earth radius
 * @returns {Number}
 */
GpsPoint.getEarthRadius = function () {
    return 6371000;
};

/**
 * Calculates distance (in kilometers) to GPS point
 * @param {GpsPoint} point
 * @returns {Number}
 */
GpsPoint.prototype.getDistanceTo = function (point) {

    /**
     * This gps point radians
     * @type {Number}
     */
    var thisLatitudeRadian = this.getLatitude().toRadians(),
        thisLongitudeRadian = this.getLongitude().toRadians();

    /**
     * Target gps point radians
     * @type {Number}
     */
    var pointLatitudeRadian = point.getLatitude().toRadians(),
        pointLongitudeRadian = point.getLongitude().toRadians();

    /**
     * The difference between this and the target gps points
     * @type {Number}
     */
    var latitudeDifference = pointLatitudeRadian - thisLatitudeRadian,
        longitudeDifference = pointLongitudeRadian - thisLongitudeRadian;

    /**
     * The math
     * @type {Number}
     */
    var a = Math.sin(latitudeDifference / 2) * Math.sin(latitudeDifference / 2) +
            Math.cos(thisLatitudeRadian) * Math.cos(pointLatitudeRadian) *
            Math.sin(longitudeDifference / 2) * Math.sin(longitudeDifference / 2),
        b = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

    return (GpsPoint.getEarthRadius() * b) / 1000;
};

/**
 * Customer object
 * @param customerData
 * @constructor
 */
function Customer(customerData) {

    /**
     * Customer id
     * @type {Number}
     */
    var id = parseInt(customerData.user_id);

    /**
     * Customer gps position
     * @type {GpsPoint}
     */
    var position = new GpsPoint(
        parseFloat(customerData.latitude),
        parseFloat(customerData.longitude)
    );

    /**
     * Returns customer ID
     * @returns {Number}
     */
    this.getId = function () {
        return id
    };

    /**
     * Returns customer name
     * @returns {String}
     */
    this.getName = function () {
        return customerData.name;
    };

    /**
     * Returns customer gps position
     * @returns {GpsPoint}
     */
    this.getGpsPoint = function () {
        return position
    };
}

/**
 * CustomerList object
 * @constructor
 */
function CustomerList() {
}

/**
 * Sort ascending pseudo-constant
 * @type {Number}
 */
CustomerList.SORT_ASC = 1;

/**
 * Sort descending pseudo-constant
 * @type {number}
 */
CustomerList.SORT_DESC = -1;

/**
 * Extending Array prototype
 * @type {Array}
 */
CustomerList.prototype = [];

/**
 * Sorts the list by customer id
 * @param [direction]
 * @returns {CustomerList}
 */
CustomerList.prototype.sortByCustomerId = function (direction) {
    direction = direction || CustomerList.SORT_ASC;
    return this.sort(function (a, b) {
        if (a.getId() == b.getId()) {
            return 0;
        }
        return a.getId() > b.getId() ? direction : -direction;
    })
};

/**
 * Customers list
 * @type {CustomerList|Array}
 */
var list = new CustomerList;

// Read the file line by line
require('readline')
    .createInterface({
        input: require('fs').createReadStream('./customers.json'),
        output: process.stdout,
        terminal: false
    })
    // Execute on every line
    .on('line', function (line) {
        /**
         * Customer object
         * @type {Customer}
         */
        var customer = new Customer(JSON.parse(line));

        // Check that the distance between the customer and the head office is less than or equals the maximum distance
        if (customer.getGpsPoint().getDistanceTo(headOffice) <= maximumDistance) {
            list.push(customer);
        }
    })
    // Execute when all the lines are read
    .on('close', function () {
        // Sort the list by customer id
        list.sortByCustomerId()
            // Output the result
            .forEach(function (customer) {
                process.stdout.write(
                    'Customer ID: ' + customer.getId() +
                    '; Customer name: ' + customer.getName() + '\n'
                );
            });
    });