jpaljasma/tailable-cursor.js Secret

## tailable-cursor.js
/**
 * How to subscribe for new MongoDB documents in Node.js using tailable cursor
 */

// subscriber function
var subscribe = function(){

  var args = [].slice.call(arguments);
  var next = args.pop();
  var filter = args.shift() || {};

  if('function' !== typeof next) throw('Callback function not defined');

  // connect to MongoDB
  require('mongodb').MongoClient.connect('mongodb://localhost/test', function(err, db){

    // make sure you have created capped collection "messages" on db "test"
    db.collection('messages', function(err, coll) {

      // seek to latest object
      var seekCursor = coll.find(filter).sort({$natural: -1}).limit(1);
      seekCursor.nextObject(function(err, latest) {
        if (latest) {
          filter._id = { $gt: latest._id }
        }

        // set MongoDB cursor options
        var cursorOptions = {
          tailable: true,
          awaitdata: true,
          numberOfRetries: -1
        };

        // create stream and listen
        var stream = coll.find(filter, cursorOptions).sort({$natural: -1}).stream();

        // call the callback
        stream.on('data', next);
      });
    });

  });

};

// new documents will appear in the console
subscribe( function(document) {
  console.log(document);
});
	/**
	* How to subscribe for new MongoDB documents in Node.js using tailable cursor
	*/

	// subscriber function
	var subscribe = function(){

	var args = [].slice.call(arguments);
	var next = args.pop();
	var filter = args.shift() \|\| {};

	if('function' !== typeof next) throw('Callback function not defined');

	// connect to MongoDB
	require('mongodb').MongoClient.connect('mongodb://localhost/test', function(err, db){

	// make sure you have created capped collection "messages" on db "test"
	db.collection('messages', function(err, coll) {

	// seek to latest object
	var seekCursor = coll.find(filter).sort({$natural: -1}).limit(1);
	seekCursor.nextObject(function(err, latest) {
	if (latest) {
	filter._id = { $gt: latest._id }
	}

	// set MongoDB cursor options
	var cursorOptions = {
	tailable: true,
	awaitdata: true,
	numberOfRetries: -1
	};

	// create stream and listen
	var stream = coll.find(filter, cursorOptions).sort({$natural: -1}).stream();

	// call the callback
	stream.on('data', next);
	});
	});

	});

	};

	// new documents will appear in the console
	subscribe( function(document) {
	console.log(document);
	});