Question

here is my code

db.query(str, arr, function selectCb(error, results, fields) {
            if (error) {
                return proceed(false, {errno:'010',message:error.message}, request);
            }
            var q = async.queue(function (results, callback) {
                // add the gib infor
                if (results.refertype=='G') {
                    var input={};
                    input.fields="*";
                    input.gibname=results.refername;
                    gib.getgibinternal(input, makeCallback(i));
                    function makeCallback(index) {
                        return function(gresult) {
                            results.gib=gresult.data[0];
                            callback(results);
                        }
                    }
                    // add the user info        
                } else if(results.refertype=='U') {
                    var input={};
                    input.username=results.refername;
                    input.fields="*";
                    user.getuserinternal(input, makeCallbackuser(i));
                    function makeCallbackuser(index) {
                        return function(gresult) {
                            results.user=gresult.data[0];
                            callback(results);
                        }
                    }
                } 

            }, results.length);
            // assign a callback
            q.drain = function() {
                return proceed(true, self.results, self.request);
            }
            self.results=results;

            for (var i=0; i<results.length; i++) {
                // the first console
                console.log(results[i]);
                // add some items to the queue
                q.push(results[i], function (results) {
                     results[i]=results;
                     self.results[i]=results;
                                    //the second console.
                    console.log(results);
                });
            }
            if (results.length==0) {
                return proceed(true, results, request);
            }  
        });

The out put of above code is :

// the first console
{ cardid: 30,
  cardtype: 'I',
  status: 'A',
  refername: 'admin',
  refertype: 'U' }
// the second console 
{ '1': [Circular],
  cardid: 30,
  cardtype: 'I',
  status: 'A',
  refername: 'admin',
  refertype: 'U',
  user:
   { name: 'admin',
     username: 'admin',
     deleted: 'N' } }

how this '1': [Circular], get added .?

Answer 1

This bit:

q.push(results[i], function (results) {

is the same as this (with some renaming to make it easier to track the scope):

q.push(self.results[i], function(r) {
    r[i] = r; // <------------------- Look at me!
    self.results[i] = r;
    //the second console.
    console.log(r);
});

The self.results[i] change just comes from the self.results=results; right above your for loop. The interesting part is this:

    r[i] = r;

If i is 1 you will have added a property named 1 to r whose value is r itself, hence the [Circular]. I would hazard a guess that results.length is 2 and that your function is acting as a closure over i and ending up with using the last value that i had and that’s why you get the '1' rather than a '0' property.

I see three main Things that could be causing you trouble:

• The classic closure problem with i.
• Too many things were called results so it was easy to lose track of which one you were working with.
• The circular reference: r[i] = r;.

Another possible source of confusion is that results and self.results are the same object but that might be okay.