Asynchronous loop issues illustrative example

gistfile1.js

// Illustrative case
// YEAH -- ILLUSTRATIVE OF THE FACT THAT YOU CAN ISSUE PARALLEL QUERIES TO THE DATABASE INSTEAD OF SERIAL ONES LIKE A DUMB THREADED IMPLEMENTATION THAT IS INFERIOR FOR DOING WEB SERVERS

function (recentBlogPostIds, callback) { // obviously you need this, but use callback instead of return

var results = {};
var count = 0;

for (var i = 0; i < recentBlogPostIds.length; i++) {
  var blogPostId = recentBlogPostIds[i];
  // var results = []; <-- RESETTING results IN THE FOR LOOP IS WRONG EVEN WITHOUT ASYNC!

  // Fetch from DB
  asynchronousDB.getBlogPostById(blogPostId, function(err, blogPostId, post) {
    results[blogPostId] = post;
    if (++count === recentBlogPostIds.length) callback(results);
  });
}

// Return results
// return results; <-- WRONG, THE I/O HASN'T HAPPENED YET

}