couchdb_advertiser_daily_impressions.js

// Map function
function(doc) {
  // Format date to yyyy mm dd
  var date = doc.created_at.replace(/T|-/g, ' ').replace('+', ' +');
  
  // return advertiser, date
  emit(doc.accounts.advertiser, date.substring(0,10))
}

// Reduce function
function(keys, values) {
  var results = {};

  for (var i=0; i < values.length; i++) {
     var current = values[i];
     if (!results[current]) {
       results[current] = 0 ;
     }
     results[current]++;
  }
  return results;
}