Simple ES Query

gistfile1.js

eventsource
  .fromStreams(['os'], 'statistics')
  .run({
    $init: function(state){
     state.count = 0;
     return state;
    },
    $completed: function(state){
     return state;
    },
    os: function(state, item){
      state.count += 1;
      return state;
    }}, function(err, data){
      done(null,data);
    }
  );