get value variable outside fb.api with callback

Question

I know the problem with ajax and return variables, I was reading in stackoverflow about this, I know that I have to use a callback function, but in my case didn't work, of course something I'm making wrong

My code is this:

var id_user=get_id_user_login();//undefined??????????

function get_id_user_login(){
    FB.api(                                                
         '/me',                     
          {fields:'id'},
          function(response){//callback       
                 console.log(response.id);//OK
                 return response.id;
           }
     );             
};

Answer 1

You can´t just return the value because it´s asynchronous. Try this:

function customFunction(id) {
    console.log(id);
}

function get_id_user_login(){
    FB.api(                                                
         '/me',                     
          {fields:'id'},
          function(response){   
                 customFunction(response.id);
           }
     );             
};

get_id_user_login();