Promises Exercise 3 Possible Solution

iss-promise.js

var request = require('request');
var prompt = require('prompt');
var Promise = require('bluebird');
var promptPromisified  = Promise.promisifyAll(prompt);
var requestPromisified = Promise.promisify(request);

//necessary function for distanceTo
Number.prototype.toRadians = function() {
    return this * Math.PI / 180;
}


//Returns distance between point1 and point2;
var distanceTo = function(point1, point2, radius) {
    radius = (radius === undefined) ? 6371 : Number(radius);

    var R = radius;
    var φ1 = point1.lat.toRadians(),  λ1 = point1.lng.toRadians();
    var φ2 = point2.lat.toRadians(), λ2 = point2.lng.toRadians();
    var Δφ = φ2 - φ1;
    var Δλ = λ2 - λ1;

    var a = Math.sin(Δφ/2) * Math.sin(Δφ/2) +
            Math.cos(φ1) * Math.cos(φ2) *
            Math.sin(Δλ/2) * Math.sin(Δλ/2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    var d = R * c;

    return d;
};


// // Wishful thinking (the code below does NOT work)
// var userLocation = prompt.get(['location']);
// var userGeoLocation = request('https://maps.googleapis.com/maps/api/geocode/json?address='+userInput);
// var issPosition = request('http://api.open-notify.org/iss-now.json');
// //var dist=  distance(.....);
// //console.log("your distance is " + distance);
// // End of wishful thinking (the code above does NOT work)

// Ask the user for their location, and tell them the lat/long for that location
function getUserLatLong() {
    return promptPromisified.getAsync(['location']).then(
        function(result) {
            return requestPromisified('https://maps.googleapis.com/maps/api/geocode/json?key=AIzaSyCqB6bDHnvEmYxcRm5qg6yso2V9Q4MbOiE&address='+result.location);
        }
    ).then(
        function(result2) {
            var body = result2[1];
            var location = JSON.parse(body).results[0].geometry.location;
            // console.log("Your location is: ");
            // console.log(location);
            return location;
        }
    );
}

function getIssLatLong() {
    return requestPromisified('http://api.open-notify.org/iss-now.json').then(
        function(result) {
            var body = result[1];
            var issLocation = JSON.parse(body);
            
            return {lat: issLocation.iss_position.latitude, lng: issLocation.iss_position.longitude};
        }
    );
}

function getDistanceToIss() {
    var userLocPromise = getUserLatLong();
    var issLocPromise = getIssLatLong();
    
    return Promise.join(userLocPromise, issLocPromise, function(userLoc, issLoc) {
        var distance = distanceTo(userLoc, issLoc);
        return distance;
    });    
}

getDistanceToIss().then(
    function(distance) {
        console.log("The distance in metres is: " + distance);
    }
);