Javascript function return always undefined

Question

new to JS so i'm expecting my bug is very easy to fix.

So i've go a function in a users.js file :

exports.authenticate = function(user){
User.findOne({
    'username':user.username,
    'password':user.password,
},'username', function (err, dbuser) {
        if (err) return handleError(err);
        console.log(Boolean(dbuser));
        return Boolean(dbuser);

    });
}

So i return the value of my dbuser as a boolean : true if he exists, else false. Quite simple no ? But there come the trap..

var userClass = require('./users.js');
var myUser = userClass.create('xxazeddax','azezaeazeazeaz','mazeazeazezaeaze');
var authent  = userClass.authenticate(myUser);
console.log(authent);

Here I'm expecting a boolean value because it's the only thing authenticate() can return.. But not , I got undefined. Please, where did I got wrong ?

Answer 1

Your function(user) aka as authenticate does not return anything your other function function (err, dbuser) is a callback function it means that it will be executed when the request is completed, however, since it is a callback funtion this means that the function(err, dbuser) was not meant to be executed sequentially.

I recommend you this article to understand what is happening

http://www.impressivewebs.com/callback-functions-javascript/

I quick way to see what is going on change your code in this way:

function(user){
     User.findOne({'username':user.username,'password':user.password},'username', 
     function (err, dbuser) {
        if (err) return handleError(err);
        console.log(Boolean(dbuser));
        return Boolean(dbuser);
    });
  return true; //<-- authenticate will always return true
}