mongoose - Mongooose query where ObjectId is null? -

how can search document doing .findone objectid field not set? cannot find if should searching on null or undefined or else.

in example below, i'm trying find document "email" value known userid has not yet been set:

var joinrequest = new mongoose.schema({     email: { type: string, unique: true, lowercase: true, trim: true },     code: { type: string, uppercase: true, trim: true, select: false  },     lastsent: { type: date },     userid: { type: mongoose.schema.types.objectid, select: false } }); 

then again, can objectid field ever null? should use string here?

few things undefined in context of mongodb

properties value undefined not stored. following have no a property

db.insert({a : undefined}) 

however arrays undefined values converted null

db.insert({a : [undefined]}) //stores {a : [null]} 

also undefined has weird behaviors when used condition

db.users.find({a : undefined}) //finds db.users.findone({a : undefined}) //always returns first document (which problem you) db.users.update({a : undefined}, {a : true}) //only updates documents no property 

so avoid use of undefined , pretend doesn't exist. use null instead since stored , does't dropped condition.

so example

db.users.insert({email : "email@domain.com", userid : null}); db.users.findone({email : "email@domain.com", userid : null}); 

if decide use undefined though this

db.users.insert({email : "email@domain.com"}); db.users.findone({email : "email@domain.com", userid : { exists : false }}); //works null 

http://docs.mongodb.org/manual/reference/operator/query/exists/