i'm trying create todo app using node.js, mongoose , backbone learning purposes. till defined these models: var taskschema = new mongoose.schema({ title: { type:string }, content: { type:string } , created: {type:date, 'default':date.now}, due: {type:date}, accountid: {type:mongoose.schema.objectid} }); var task = mongoose.model('task',taskschema); var accountschema = new mongoose.schema({ email: { type:string, unique: true}, password: { type:string } , name: { first: {type:string}, last: { type:string } }, birthday: { day: {type:number, min:1, max:31, required:false}, month: {type:number, min:1, max:12, required:false}, year: {type:number} }, photourl: {type:string}, biography:{type:string}, tasks:[task] }); var account = mongoose.model('account',accountschema); in addition, have following method adding task : var enter_new_task = function(options,callback){