Node.js get the return value of a function

Question

I just started working on node.js and getting to know its concepts, I am having a little trouble understanding callbacks,what I am trying to do is call function getUserBranch() in the function getOffers() .

I read that because of node.js async nature its better to use a callback function to get the desired data once the complete execution is done.

Now I am having trouble retrieving the value that getUserBranch is returning,I have no proper idea how to do it, well the callback function has the value but how do I get the value from there?

file2.js

var getUserBranch = function(email,callback) {


client.execute('SELECT * from branch WHERE email=?', [ email ], function(
        err, data, fields) {
    if (err)

        console.log("error");
    else
        console.log('The solution is in branch: \n', data);
    res = data.rows[0];
    return callback(res);
});

}

file1.js

var getOffers = function (email) {

   var branchObj = require('./file2.js');
   var branchList = branchObj.getUserBranch(email,getList));
   return branchList;
};

var getList = function(res){
  var results=res;
  return results;
}

Answer 1

In async call work with callback function in the stack. Look this:

var getUserBranch = function(email,callback) {
    client.execute('SELECT * from branch WHERE email=?', [ email ], function(err, data, fields) {
        if (err)
            console.log("error");
        else{
            console.log('The solution is in branch: \n', data);
            /* This data stack 3  */
            callback(data.rows[0];);
        }
    });
};

var getOffers = function (email, callback) {
    var branchObj = require('./file2.js');
    branchObj.getUserBranch(email, function(data){
        /* This data stack 2  */
        callback(data);
    });
};

function anyFunction(){
    getOffers("xx@xxx.com", function(data){
        /* This data stack 1  */
        console.log(data);
    });
}