trying to fetch the data in a nested arrays from mongodb in node js

Question

trying to fetch the data in a nested arrays from mongodb in node js

exports.cities = async (req, res, next) => {
  MongoClient.connect(url, function (err, db) {
    if (err)
      res.send(err);
    let dbo = db.db(DATABASE);
    const { country_code, state_code } = req.body;
    dbo.collection("countries").find({iso2:country_code}).toArray(function (err, result) {
      //res.json(result);
      for(let i=0; i<result.length; i++){
        for(let j=0; j<result[i].states.state_code.length; j++){
              if(result[i].states[j].state_code == result[AP]){
                res.json(result[i].states[j])
              }
        }
        //res.json(result[i]);
      }
    })
  });
}

enter image description here

Answer 1

You shouldn't connect to mongo in HTTP request callbacks, connect to it once and re-use that connection.

const mongoClient = new MongoClient(url, { useNewUrlParser: true });

mongoClient.connect((err) => {
  if (err) throw err;

  // Available via req.app.locals.db.
  app.locals.db = mongoClient.db('your-database');

  app.listen(3000); 
});

Instead of looping over the cursor you can just call toArray, I recommend you don't format your data to a string on the server, instead pass the array back as JSON to the client and let the client render it out however it wants:

app.route('/results').get(async (req, res) => {
  const { db } = req.app.locals;
  const results = await db.collection('results').toArray();
  res.status(200).json(results);
});