app.js

    var http = require('http');
    var MongoClient = require('mongodb').MongoClient;
    var assert = require('assert');
    var ObjectId = require('mongodb').ObjectID;
    var mongoURL = 'mongodb://localhost:27017/tweets';
    var fs = require('fs');
    var http = require('http');
    var url = require('url') ;
    var util = require("util");
    // NEVER use a Sync function except at start-up!
    index = fs.readFileSync(__dirname + '/map.html');


    //Lets define a port we want to listen to
    const PORT=4040;
    var itemsProcessed = 0;
    var total =0;
    var queryData;
    const COLLECTION = 'tweets';
// Send index.html to all requests
var app = http.createServer(function(req, res) {
    console.log("creating server");
    res.writeHead(200, {'Content-Type': 'text/html'});

    queryData = url.parse(req.url, true).query;
    res.end(index);
    //start();

});
app.listen(PORT);
// Socket.io server listens to our app
var io = require('socket.io').listen(app);

function start(){
  console.log("starting");
  MongoClient.connect(mongoURL, function(err, db) {
    assert.equal(null, err);
    console.log(JSON.stringify(queryData));
    if(queryData){
      if(queryData.page =="stream"){
        console.log("starting stream");
        findTweetsStream(db);
      }
      else if(queryData.page =="data"){
        console.log("starting stats");
        showStats(db);
      }
    }
  });
}

// Emit welcome message on connection
io.on('connection', function(socket) {
    // Use socket to communicate with this particular client only, sending it it's own id
    MongoClient.connect(mongoURL, function(err, db) {
      db.collection(COLLECTION).count(function(err, count){
        socket.emit('welcome', { message: 'Welcome! '+count+' tweets tracked', id: socket.id });
      });
    });
    start();

});



var showStats = function(db) {
  var html = '';
  db.collection(COLLECTION).count(function(err, count){
    io.emit('data', count);
    db.stats(function(err, stats){
      io.emit('data', stats);
      db.close();
    });
  });
};

var findTweetsStream = function(db, callback,res) {

   var cursor =db.collection(COLLECTION).find({geo:{$ne:null }});
  // var html = '<h2> Results '+queryData.search+' </h2>';
   var counter=0;
   cursor.on('data', function(tweet) {
     if (tweet != null) {
       var tweettext = tweet.text.toLowerCase();
       console.log(tweettext);
       //var data = { cord : tweet.geo.coordinates , eu : 'i' };
       //io.emit('time', data);

         var data = { cord : tweet.geo.coordinates , eu : 'x' };
         io.emit('time', data);


       if(tweettext.indexOf('brexit')>0){
         data = { cord : tweet.geo.coordinates , eu : 'o' };
         io.emit('time', data);

       }
       if(tweettext.indexOf('bremain')>0){
         data = { cord : tweet.geo.coordinates , eu : 'i' };
         io.emit('time', data);

       }


        console.log(counter++);

      }
    });

    cursor.once('end', function() {
      db.close();
    });
};