wrong-async.js

var async = require('async');
var obj = ["a", "b", "c"];

function done()
{
    console.log("Done");
}

function output(key, n, cb)
{
    console.log(key);
    console.log(n);
    cb();
}

function m(obj, callback) {

    var tasks = Object.keys(obj).length;
    var arr = ['one', 'two', 'three'];

    for (key in obj) {
        tasks--;
        async.eachSeries(arr, function(n, cb) {
            // do stuff here.
            if (Math.random() > 0.5) {
                setTimeout(output, 1000, key, n, cb);
            } else {
                cb();
            }
        }, function(err) {
            // operations after array iteration completed.
            if (tasks === 0) {
                // All tasks done, return to callback
                callback();
            }
        });
    }
}

m(obj, done);

console.log("Where should this be");