try{
    var db = connect('admin');
    if(db.system.users.find({'user':'esb'}).count() == 0){
        print('Ready to addUser...');
        db.createUser({ user: 'esb', pwd: 'esb', roles: [ { role:"readWriteAnyDatabase", db: "admin" } ] });
    }else{
        print('Already exist user.')
    }
}catch(err){
    print('Error occured:' + err);
}