MongoDB Product MapReduce 4

gistfile1.js

map = function map() {
      emit(this.type, {productIds : [this._id]})
}

reduce = function reduce(key, values) {
    var productIds = [];

    var result = { productIds:[] };

    values.forEach(function(value) {
    	value.productIds.forEach(function(idValue){
    		productIds.push(idValue);
    	});
    });

    result.productIds = productIds;

    return result;
}

> db.product.mapReduce(map,reduce,{out:"productMapReduce4"})
{
	"result" : "productMapReduce4",
	"timeMillis" : 70,
	"counts" : {
		"input" : 6,
		"emit" : 6,
		"reduce" : 2,
		"output" : 2
	},
	"ok" : 1,
}

> db.productMapReduce4.find().pretty()
{
	"_id" : "Shirt",
	"value" : {
		"productIds" : [
			ObjectId("4faec33dd57e4ace158b7e9f"),
			ObjectId("4faec64bd57e4ace158b7ea0"),
			ObjectId("4faec65ad57e4ace158b7ea1")
		]
	}
}
{
	"_id" : "Sweat Shirt",
	"value" : {
		"productIds" : [
			ObjectId("4faf8768d001a2b51cf047a0"),
			ObjectId("4faf877ad001a2b51cf047a1"),
			ObjectId("4faf878dd001a2b51cf047a2")
		]
	}
}