made some changes to mongo connection

src/app.ts

@@ -1,6 +1,3 @@
-/**
- * Module dependencies.
- */
 import * as express from "express";
 import * as compression from "compression";  // compresses requests
 import * as session from "express-session";
@@ -13,50 +10,38 @@ import * as flash from "express-flash";
 import * as path from "path";
 import * as mongoose from "mongoose";
 import * as passport from "passport";
-import expressValidator = require("express-validator");
+import * as expressValidator from "express-validator";
+import * as bluebird from "bluebird";
 
 const MongoStore = mongo(session);
 
-/**
- * Load environment variables from .env file, where API keys and passwords are configured.
- */
+// Load environment variables from .env file, where API keys and passwords are configured
 dotenv.config({ path: ".env.example" });
 
-
-/**
- * Controllers (route handlers).
- */
+// Controllers (route handlers)
 import * as homeController from "./controllers/home";
 import * as userController from "./controllers/user";
 import * as apiController from "./controllers/api";
 import * as contactController from "./controllers/contact";
 
-/**
- * API keys and Passport configuration.
- */
+
+// API keys and Passport configuration
 import * as passportConfig from "./config/passport";
 
-/**
- * Create Express server.
- */
+// Create Express server
 const app = express();
 
-/**
- * Connect to MongoDB.
- */
-// mongoose.Promise = global.Promise;
-mongoose.connect(process.env.MONGODB_URI || process.env.MONGOLAB_URI);
-
-mongoose.connection.on("error", () => {
-  console.log("MongoDB connection error. Please make sure MongoDB is running.");
-  process.exit();
+// Connect to MongoDB
+const mongoUrl = process.env.MONGOLAB_URI;
+(<any>mongoose).Promise = bluebird;
+mongoose.connect(mongoUrl, {useMongoClient: true}).then(
+  () => { /** ready to use. The `mongoose.connect()` promise resolves to undefined. */ },
+).catch(err => {
+  console.log("MongoDB connection error. Please make sure MongoDB is running. " + err);
+  // process.exit();
 });
 
-
-
-/**
- * Express configuration.
- */
+// Express configuration
 app.set("port", process.env.PORT || 3000);
 app.set("views", path.join(__dirname, "../views"));
 app.set("view engine", "pug");
@@ -70,7 +55,7 @@ app.use(session({
   saveUninitialized: true,
   secret: process.env.SESSION_SECRET,
   store: new MongoStore({
-    url: process.env.MONGODB_URI || process.env.MONGOLAB_URI,
+    url: mongoUrl,
     autoReconnect: true
   })
 }));
@@ -86,13 +71,13 @@ app.use((req, res, next) => {
 app.use((req, res, next) => {
   // After successful login, redirect back to the intended page
   if (!req.user &&
-      req.path !== "/login" &&
-      req.path !== "/signup" &&
-      !req.path.match(/^\/auth/) &&
-      !req.path.match(/\./)) {
+    req.path !== "/login" &&
+    req.path !== "/signup" &&
+    !req.path.match(/^\/auth/) &&
+    !req.path.match(/\./)) {
     req.session.returnTo = req.path;
   } else if (req.user &&
-      req.path == "/account") {
+    req.path == "/account") {
     req.session.returnTo = req.path;
   }
   next();