Angular Service Wrapper.js

// Imagine your code structure is something like this.

// start
...
function sendSms() {
// Implementation
}
..
//end

// This is how it can wrapped in a Angular Service

var smsService = angular.module('app.services')

smsService.factory('smsService',
    [function(){
      // start
      ...
      function sendSms() {
      // Implementation
      }
      ..
      //end
      
      return {
        sendSms: sendSms
      }
    
    }]);

twillio.api_key.js

// Configuration for Twilio SMS API.

module.exports = {
  // Production
  TWILIO_ACCOUNT_SID: 'ACba5e5ecc95blahblah79bbc17d93f62e08',
  TWILIO_AUTH_TOKEN: '0331cbb3628fbe5blahblahf983e069009',
  // TWILIO_NUMBER: '+14086375837'
  TWILIO_NUMBER: '+12513330209'

  // Testing
  // TWILIO_ACCOUNT_SID: 'AC3724c2b73b5blahblahb890d2d358eb188b',
  // TWILIO_AUTH_TOKEN: '6d904fbc7c33blahblahae60f8fcec78e9',
  // TWILIO_NUMBER: '+15005550006'

}

twillio.config.js

var SMS_CONFIG = require('./twilio.api_key.js');

var cfg = {};

// A random string that will help generate secure one-time passwords and
// HTTP sessions
cfg.secret = process.env.APP_SECRET || 'keyboard cat';

// Your Twilio account SID and auth token, both found at:
// https://www.twilio.com/user/account
//
// A good practice is to store these string values as system environment
// variables, and load them from there as we are doing below. Alternately,
// you could hard code these values here as strings.

cfg.accountSid = process.env.TWILIO_ACCOUNT_SID || SMS_CONFIG.TWILIO_ACCOUNT_SID;
cfg.authToken = process.env.TWILIO_AUTH_TOKEN   || SMS_CONFIG.TWILIO_AUTH_TOKEN;
cfg.sendingNumber = process.env.TWILIO_NUMBER   || SMS_CONFIG.TWILIO_NUMBER;

var requiredConfig = [cfg.accountSid, cfg.authToken, cfg.sendingNumber];
var isConfigured = requiredConfig.every(function(configValue) {
  return configValue || false;
});

if (!isConfigured) {
  var errorMessage =
    'TWILIO_ACCOUNT_SID, TWILIO_AUTH_TOKEN, and TWILIO_NUMBER must be set.';

  throw new Error(errorMessage);
}

// Export configuration object
module.exports = cfg;

twillio_controller.js

var express       = require('express');
var twilioService = require('../services/twilio_service.js');
var router        = express.Router();

router.post('/sendmsg', function(req, res, next) {
  var msg = req.body;
  var resp = {};

  if (!msg || !msg.to || !msg.text) {
    resp.status = "error";
    resp.message = "invalid data";
    res.json(resp);
    return 1;
    //next();
  }

  twilioService.sendSms(msg.to, msg.text, function(err, data){
    if(err) {
      resp.status = "error";
      resp.message = err;
    } else {
      resp.status = "success";
      resp.message = data.sid;
    }
    res.json(resp);
    //next();
  });
});

module.exports = router;

twillio_service.js

var config = require('../../config/twilio.config.js');
var client = require('twilio')(config.accountSid, config.authToken);

module.exports.sendSms = function(to, message, callback) {

    console.log("==== Sending SMS ====");
    console.log("To: " + to );
    console.log("Msg: " + message );
    console.log("==== End Sending SMS ====");

  client.messages.create({
    body: message,
    to: to,
    from: config.sendingNumber
//  mediaUrl: imageUrl
  }, function(err, data) {
    if (err) {
      console.error('Could not notify user');
      console.error(err);
      // resp.status = "error";
      // resp.message = err;
    } else {
      console.log('User notified');
      // resp.status = "success";
      // resp.message = data.sid;
    }
    callback(err, data);
  });
};