transactions.js

var mongo = require('../lib/mongodb'),
    sys = require('sys');

    var host = process.env['MONGO_NODE_DRIVER_HOST'] != null ? process.env['MONGO_NODE_DRIVER_HOST'] : 'localhost';
    var port = process.env['MONGO_NODE_DRIVER_PORT'] != null ? process.env['MONGO_NODE_DRIVER_PORT'] : mongo.Connection.DEF
AULT_PORT;

sys.puts("Connecting to " + host + ":" + port);
var db = new mongo.Db('test', new mongo.Server(host, port, {}), {});
db.open(function(err, db) {
    db.collection('transactions', function(err, collection) {
        var name_letter = 'v';
        var map = function() { emit('sum', this.amount) }

       // var reduce = function (k, vals) {var sum = 0;for(var i in vals) sum += vals[i];return (sum / vals.length); };
       var reduce = function(k, vals) { var sum = 0; for (var i in vals) { sum += vals[i] } return sum; }

        collection.mapReduce(map, reduce, function(err, result) {
            if (err) {
                sys.puts(JSON.stringify(err));
            } else {
                result.findOne({'_id':'sum'}, function(err, scores) {
                    if (err) {
                       sys.puts('Err in results');
                    }
                    sys.puts('Scores: ' + JSON.stringify(scores));
                    process.exit();
                });
                sys.puts('Mapreduce done');
            }



        });
    });

});