let MongoClient = require('mongodb').MongoClient;
let url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
  if (err) throw err;
  let dbo = db.db("mydb");
  /*Return only the documents where the address starts with an "S":*/
  let query = { address: /^S/ };
  dbo.collection("customers").find(query).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
  });
});