@riskyvaibhav/lat-long-to-km/index.js

This module takes in lat long of two locations and returns the distance between them in Kilometres.

'use strict';

/**
 * Adds commas to a number
 * @param {number} lat1
 * @param {number} lon1
 * @param {number} lat2
 * @param {number} lon2
 * @return {number}
 */


module.exports = function(lat1,lon1,lat2,lon2) {
    var R = 6371; // Radius of the earth in km
    var dLat = deg2rad(lat2-lat1);  // deg2rad below
    var dLon = deg2rad(lon2-lon1);
    var a =
        Math.sin(dLat/2) * Math.sin(dLat/2) +
        Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) *
        Math.sin(dLon/2) * Math.sin(dLon/2)
    ;
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    var d = R * c; // Distance in km
    return d;
}

function deg2rad(deg) {
    return deg * (Math.PI/180)
}