Calling getParcourList returns undefined all the time

gistfile1.txt

var getParcourList = function(userId){
 
   GeneralReference.findOne({ id: userId}, function(err, result){
 
     if(err){
       console.log("error in save: " + err);
       return "No Document found: " + err; 
     }else{
       //console.log(JSON.strinresult.parcours);
       return result.parcours; 
     }      
  });
   
}

app.get("/parcour/list/:userId", function(req, res){
     
     var json = mongooseLogic.getParcourList(req.params.userId);
     if(json === undefined){
         console.log('No data');
         res.json('No data');
     }else{
         console.log(json);
         res.json(json)
     }
     

    });