added mapReduce

index.js

@@ -10,3 +10,14 @@ Mongo.Collection.prototype.aggregate = function(pipelines, options) {
   }
   return wrapAsync(coll.aggregate.bind(coll))(pipelines, options);
 }
+Mongo.Collection.prototype.mapReduce = function(mapFunction, reduceFunction, options) {
+  var coll;
+  if (this.rawCollection) {
+    // >= Meteor 1.0.4
+    coll = this.rawCollection();
+  } else {
+	// < Meteor 1.0.4
+    coll = this._getCollection();
+  }
+  return wrapAsync(coll.mapReduce.bind(coll))(mapFunction, reduceFunction, options);
+}

test.js

@@ -39,4 +39,27 @@ Tinytest.add("using some options", function(test) {
   ], options);
 
   test.equal(typeof result[0]['$cursor'], 'object');
-});
+});
+
+Tinytest.add("method mapReduce signature", function(test) {
+  var coll = new Mongo.Collection(Random.id());
+  test.equal(typeof coll.mapReduce, 'function');
+});
+
+Tinytest.add("let's mapReduce", function(test) {
+  var coll = new Mongo.Collection(Random.id());
+  coll.insert({group: 1, value: 10});
+  coll.insert({group: 1, value: 100});
+  coll.insert({group: 2, value: 1000});
+
+  var mapFunction1 = function() {
+    emit(this.group, this.value);
+  };
+  var reduceFunction1 = function(keyGroupId, values) {
+    return Array.sum(values);
+  };
+
+  var result = coll.mapReduce(mapFunction1, reduceFunction1, { out: { inline: 1 } })
+
+  test.equal(result, [{"_id":1,"value":110},{"_id":2,"value":1000}]);
+});