NodeJS + MongoDB

gistfile1.js

var MongoClient = require('mongodb').MongoClient;

MongoClient.connect('mongodb://localhost:27017/weather', function(err, db) {

  if(err) throw err;

  var map = function() {
    emit(this["State"], 1);
  }

  var reduce = function(key, values) {
    return Array.sum(values);
  }

  db.collection('data').mapReduce(map, reduce, {out: {inline: false}}, function(err, collection){

    if(err) throw err;

    console.dir(collection);
    db.close();
  });

  console.dir("Calling, be patient please...");
});

results: 

'Calling, be patient please...'
[ { _id: 'California', value: 744 },
  { _id: 'Florida', value: 733 },
  { _id: 'New Mexico', value: 742 },
  { _id: 'Vermont', value: 744 } ]