mongouniversity-hw-3.2_3.3.js

// 3.2
posts.insert(post, function (err, result) {
    "use strict";

    if (!err) {
        console.log("Inserted new post");
        return callback(null, permalink);
    }

    return callback(err, null);
});

// 3.3
var post = this.getPostByPermalink(permalink, function (err, post) {
	if (err) return callback(err, null);
	
	posts.update({_id: post._id}, {$addToSet: {'comments': comment}}, function (err, result) {
		"use strict";

		if (!err) {
		        console.log("Inserted new comment");
		        return callback(null, result[0]);
		} else {
			return callback(err, null);
		}
    	});
});