index.js

const MongoClient = require('mongodb').MongoClient;
// Initialize authentication details required for database connection
const auth = {
  user: process.env.user,
  password: process.env.password
}; 
// Initialize global variable to store database connection for reuse in future calls
let db = null;
const loadDB = async () => {
// If database client exists, reuse it  
  if (db) {
    return db;
  }
// Otherwise create new connection  
  const client = await MongoClient.connect(
    process.env.url,
    {
      auth: auth
    }
  );
// Select tacos database
  db = client.db('tacos');
  return db;
};
module.exports = async function(context, req) {
  try {
// Get database connection
    const database = await loadDB();
// Retrieve all items in the Recipes collection 
    let recipes = await database
      .collection('Recipes')
      .find()
      .toArray();
// Return a json object with the array of recipes 
    context.res = {
      body: { items: recipes }
    };
  } catch (error) {
    context.log(`Error code: ${error.code} message: ${error.message}`);
// Return an error message and Internal Server Error status code
    context.res = {
      status: 500,
      body: { message: 'An error has occured, please try again later' }
    };
  }
};