cant return a value outside the query. mongoose

Question

i'm new to node js, i'm using restify and mongoose. so, i try to return some value when i found the data and return null when data not found. here is my code:

getUsers = function (user, pass, urole){
      var data = '';
      Publisher.findOne({username:user, password:pass, role:urole},function(err, success){
         if (err){}
         if (!success){
           //when data not found
           data = 'null';
         }else{
           //when data found
           data = 'found'; 
         }
     });
     return data;
}

and i want to call the function and assign to the variable.

var user = getUsers(user,pass,urole)
console.log(user)

but the result is undefined.

Answer 1

The findOne is async function, please put return data into the callback function, also return date through callback function

getUsers = function (user, pass, urole, callback){
      var data = '';
      Publisher.findOne({username:user, password:pass, role:urole},function(err, success){
         if (err){}
         if (!success){
           //when data not found
           data = 'null';
         }else{
           //when data found
           data = 'found'; 
         }
         callback && callback(data);
     });
}

getUsers(user, pass, urole, function(data) {
    console.log(data);
});