Lambda function to set nest humidity

'use strict';
const https = require('https');
const queryString = require('querystring');
const url = require('url');
const nest = require('nest');
const util = require('util');

const postalCode = "22902";
const username = "bhspencer@gmail.com";
const password = "youcanthack1T@";

var lambdaCallback = null;

exports.handler = (event, context, callback) => {
    lambdaCallback = callback;
    getCurrentWeather(onGotCurrentWeather);
};

function onGotCurrentWeather(weather) {
    var currentOutsideTempC = weather.now.current_temperature;
    var currentOutsideTempF = convertCtoF(currentOutsideTempC);
    var newTargetHumidity = calculateTargetHumidity(currentOutsideTempF);
    loginAndSetTargetHumidity(newTargetHumidity);
}
function loginAndSetTargetHumidity(newTargetHumidity) {
    nest.login(username, password, function (err, data) {
        if (err) {
            console.log(err.message);
            process.exit(1);
            return;
        }
        console.log('Logged in.');
        nest.fetchStatus(function (data) {
            for (var deviceId in data.device) {
                if (data.device.hasOwnProperty(deviceId)) {
                    var device = data.device[deviceId];
                    var currentTargetHumidity = device.target_humidity;
                    //console.log("Current device: " + JSON.stringify(device));
                    if (currentTargetHumidity !== newTargetHumidity) {
                        nest.setHumidity(deviceId, newTargetHumidity);
                        lambdaCallback(null, "Set humidity to " + newTargetHumidity);
                    } else {
                        lambdaCallback(null, "Target humidity is already correct at " + currentTargetHumidity);
                    }
                }
            }
        });
    });
}

function calculateTargetHumidity(temp) {
    if (temp < -20) {
        return 15;
    } else if (-20 <= temp && temp < -10) {
        return 20;
    } else if (-10 <= temp && temp < 0) {
        return 25;
    } else if (  0 <= temp && temp < 10) {
        return 30;
    } else if ( 10 <= temp && temp < 20) {
        return 35;
    } else if ( 20 <= temp && temp < 40) {
        return 40;
    } else {
        return 45;
    }
}

function convertCtoF(c) {
    return c * 9 / 5 + 32;
}

function getCurrentWeather(success) {
    var options = {
        hostname: 'home.nest.com',
        port: 443,
        path: '/api/0.1/weather/forecast/' + postalCode
    };
    doGet(options, success);
}

function doGet(options, success) {
    https.get(options, res => {
        res.setEncoding("utf8");
        let body = "";
        res.on("data", data => {
            body += data;
        });
        res.on("end", () => {
            var result = JSON.parse(body);
            success(result);
        });
    });
}