Node, Express, and Mongoose: Authentication failed error - node.js

Question

I'm new to Node/Express/Mongo/MLab and backend programming in general. I am trying to submit a post request to an MLab database and running into trouble. I think my problem is with Mongoose and MLab.
Here is my Glitch project
I'm getting error MongoDB connection error: { MongoError: Authentication failed. Why am I getting this error? Is there a problem with my mongoose.connect function and credentials? Is MLab not properly set up?
'use strict';
var express = require('express');
var mongo = require('mongodb');
var mongoose = require('mongoose');
var bodyParser = require('body-parser');
var validUrl = require('valid-url');
var dns = require("dns");
var cors = require('cors');
var app = express();
// Basic Configuration
var port = process.env.PORT || 3000;
// Hooks up app to MLab MongoDB database by using the .env variable I created
// Doesn't work. Data is not submitted to MLab and /api/shorturl/new endpoint freezes up when form is submitted
mongoose.connect(process.env.MONGODB_URI, {useMongoClient: true});
/*
Also doesn't work
mongoose.connect(process.env.MONGODB_URI, {
"auth":{"authSource": "admin"},
"user": "admin",
"pass": "password"
});
*/
// Should allow us to use promises with mongoose
mongoose.Promise = global.Promise;
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'MongoDB connection error:'));
// Sets up a Schema for the DB
var urlSchema = new mongoose.Schema({
url: String,
shortenedUrl: String
});
// Sets up a model for the DB
var Url = mongoose.model("Url", urlSchema);
app.use(cors());
/** this project needs to parse POST bodies **/
// you should mount the body-parser here
var urlencodedParser = bodyParser.urlencoded({ extended: false });
app.use(bodyParser.json()); // support json encoded bodies
app.use(bodyParser.urlencoded({ extended: true })); // support encoded bodies
app.use('/public', express.static(process.cwd() + '/public'));
// parse application/x-www-form-urlencoded
app.get('/', function(req, res){
res.sendFile(process.cwd() + '/views/index.html');
});
app.get("/api/shorturl/new", function (req, res) {
res.sendFile(process.cwd() + '/views/form.html');
//res.send({hi: "hi"});
});
app.post("/api/shorturl/new", urlencodedParser, function (req,res) {
// Gets URL from form
//var url = req.body.url;
//console.log(url);
var myData = new Url(req.body);
console.log("myData : " + myData);
myData.save()
.then(item => {
res.send("Successfully saved to DB");
})
.catch(err => {
res.status(400).send("Unable to save to DB");
});
});
app.listen(port, function () {
console.log('Node.js listening ...');
});

Answer 1

As other people have commented the code itself looks like it should work.
so the immediate suspect is the URI,
obviously you are not going to post the full string for all of us to see, but one theory that comes to mind is your password having characters that need encoding,
try using javascripts encodeURIComponent on the password.