getCats.js

'use strict';
const Express = require('express');
const Mongoose = require('mongoose');

const app = Express();
Mongoose.connect('mongodb://localhost/test', { useMongoClient: true });
Mongoose.Promise = global.Promise;

const Cat = Mongoose.model('Cat', { name: String });

app.get('/cats', async (req, res, next) => {
    // this route simply list the content of the 'Cat' collection

    try {
        const cats = await Cat.find().exec(); // using await syntax make it much simpler here
        return res.json(cats);
    }
    catch (e) {
        return next(e);
    }
});

app.listen(9090, () => {

    console.log('server running on port 9090');
});