Users = mongoose.UserSchema;
ApiUserSchema;
Users.find(function(err,users){
    //for each user that mongoose finds,
    //I want to convert from UserSchema to "ApiUserSchema"
    //Something like the following:
    newUsers = users.ToApiUserSchema();
    console.log(newUsers);
})

function toApiUserSchema(user){
     username = user.username;
     email = user.email;
     someAggregate = user.Username + user.Email;
     .......and so on.....;
}

var userSchema = new mongoose.Schema({
    username: String,
    email: String,
    password: Number
})

userSchema.statics.toApiUserSchema = function(data) {
    return data.map(function(user) {
        return {
            email: user.email,
            username: user.username,
            emailAndUsername: user.email + user.username
        }
    })
}

var User = mongoose.model('User', userSchema)

User.find({}, function(err, users) {
    console.log(User.toApiUserSchema(users))
})