mongo-demo.js

const express = require('express');
const mongodb = require('mongodb');
const app = express();

function to(promise) {
  if (!(promise instanceof Promise)) {
    promise = Promise.resolve(promise);
  }

  return promise.then(res => [null, res]).catch(err => [err]);
}

app.get('/posts', async (req, res) => {
  let err, client;
  [err, client] = await to(mongodb.connect('mongodb://localhost', { useNewUrlParser: true }));

  if (err) {

  }

  const db = client.db('blog');

  const posts = await db.collection('Post').find().limit(10).toArray();

  res.json({ posts: posts });
});

app.get('/posts/:id', async (req, res) => {
  const client = await mongodb.connect('mongodb://localhost', { useNewUrlParser: true });
  const db = client.db('blog');

  const post = await db.collection('Post').findOne({ _id: parseInt(req.params.id) });

  res.json({ post: post });
});

app.listen(3000);