Question

I’m having troubles to return a value from a function that is inside an object’s method. How could I do this? Let me explain with code.

function ObjPerson() {

    this.getPerson = function() {

         function queryDB() {
             //run query and pass result data to success or error functions
         }

         function success(data) {
             //process data 
             return data;  
         }

         function error(errorData) {
           //process error
         }

         queryDB();
    }
  }

 var person = new ObjPerson;
 var userData = ObjPerson.getPerson();

The problem is that nothing is being returned from the getPerson() method. What would be the best way to do this?

Thanks!

Answer 1

Return the value if this is a synchronous function

function ObjPerson() {

    this.getPerson = function() {

        function queryDB() {
            //run query and pass result data to success or error functions
        }

        function success(data) {
            //process data 
            return data;  
        }

        function error(errorData) {
          //process error
        }

        return queryDB(); // HERE'S THE CHANGE
   }
 }

var person = new ObjPerson(); // always use parentheses
var userData = person.getPerson(); // ERROR: getPerson is instance function

But if this function is async, then you should be doing it a bit differently. Unfortunately you won’t be able to just call:

var userData = person.getPerson();

because by the time the assignment is made, your async call will likely not return yet… So your userData assignment should be assigned after the async call. (tell us what async lib are you using)

Other code smells in your example

But your code has other smells as well. Your inner functions queryDB, success and error functions are defined within closure and for the sake of readability they should be defined as local scope variables:

var success = function (data) {
    // process data
    return data;
}