Utilizing express.js alongside the native MongoDB driver: A comprehensive guide

I'm facing difficulties when attempting a simple mongoDB query from my express app:

app.js

var express = require('express');
  var routes = require('./routes');
  var user = require('./routes/user');
  var http = require('http');
  var path = require('path');
  var mongourl = ''; // omitted on SO
  var MongoClient = require('mongodb').MongoClient;
  var dbInstance;

  MongoClient.connect(mongourl, function(err, db) {
      db.on('open', function(){
          dbInstance = db;
      })
  });


  app.get('/', routes.index(dbInstance));

  http.createServer(app).listen(app.get('port'), function(){

  });
  

routes/index.js

exports.index = function(db){
    return function(req, res){

    }

  };
  

Am I correct in understanding that the parameter for 'exports.index' is a database instance? If so, why am I unable to perform db.getCollectionNames()?

How can I effectively work with the database instance in my route?

Answer №1

Asynchronous behavior is a core feature of node.js. This means that in the context of MongoClient.connect(), both db and dbInstance are created within the callback function, not outside of it. Therefore, your code structure should be similar to the following:

MongoClient.connect(mongourl, function(err, db) {
    ...
    app.get( '/', routes.index( db ) );
    ...
});

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