MongoDB - String to ObjectID and create new collection

Question

db.firmalar.find().forEach(function(obj) {
    for( var i = 0; i < obj.osgbIdleri.length; i++){ //ObjectId ARRAY
        obj.osgbIdleri[i] = ObjectId(obj.osgbIdleri[i]);
    }  
  //out:result (firmaId.id & firmaId.osgbIdleri.id(ObjectId))
});

I want to save the string field "obj.osgbIdleri" in each document in the "Firmalar" collection as the ObjectId field. I think I can do this using "aggregation". But when using "aggregation", I can not return every object in foreach. I want to create "firmaId.id" and "firmaId.osgbIdleri.id (ObjectID)" while creating a new collection.

Answer 1

(Posted on behalf of the OP).

db.firmalar.mapReduce( 
       function() { 
           for( var i = 0; i < this.osgbIdleri.length; i++){
                this.osgbIdleri[i] = ObjectId(this.osgbIdleri[i]);
            }  
           emit(this._id, this.osgbIdleri); }, 

       function(key, values) {return value}, {  
          query:{},  
          out:"firmalarId" 
       }
    ).find()