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Showing posts from 2013

Node.JS Module Patterns using simple examples

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Slides for a recent talk at Ottawa.JS on "Node.JS Module Patterns using simple examples" are available. The slides have been updated to include a brief intro to Common.JS, examples for exporting named and anonymous functions, objects and prototypes, and an explanation of "exports" vs. "module.exports".


JavaScript Efficiencies

I'm working on an article about patterns for structuring Express.JS apps, which is taking too long, so I decided to write this instead: Here are a few tips and tricks for JavaScript programming that I like.
Comment switches Comment switches let you comment out entire blocks of code with a single character, or switch between two different blocks of code with a single character, which can be useful when prototyping.
//* 
console.log("Hello!\n");
/*/
console.log("Goodbye!\n");
// */ Removing the first slash '/' toggles between these two print statements. See the original post for more examples of comment switches.

Iterate by Counting Down You can iterate n times concisely, like this:
var n = 1000;
while (n--) { ... }
Defaulting Arguments This is a handy way to provide a default value for undefined arguments in a JavaScript function.
function foo(bar) {
   var bar = bar || "Some default";
   ...
}

Kenka Matsuri II

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Kenka Matsturi - the Battle Festival, Himeji, Japan. ©2012 Darren DeRidder

Testing Express.JS REST APIs with Mocha

My post on Testing REST APIs with RESTClient and Selenium IDE has been getting some attention, but you might also want an automated testing solution to be part of your build process.

This post will cover testing REST API's built with Express.JS, using Mocha as the test framework. Express and Mocha are both by the same author and work well together.  This technique can also be used to test Express apps in general.

In a nutshell, we'll create a test suite in Mocha that does the following:
instantiates and runs our REST API server (an Express app)sends HTTP (or HTTPS) requests to the REST APIchecks the responses for appropriate values So, let's say you've written an Express app that works as a REST API server, and now you want to automatically test it over HTTP. Assuming you have Mocha installed, and are somewhat familiar with how to use it, building a suite to test your Express app over HTTP is relatively simple.

Our example test suite is a file located at test/app_test.j…

Machine Learning in JavaScript

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I did a presentation at Ottawa JavaScript on machine learning, which covered a lot of the material in my two recent posts on Bayesian classifiers. This was new to a lot of the audience, so I made slides to step through a very simple example.

Using the "box of chocolates" analogy, the slides demonstrate how to predict if a chocolate contains nuts, depending on its colour and shape.

You can view the slides here:

http://darrenderidder.github.io/talks/MachineLearning

Parable of the Banana Leaf

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Charles and Ray Eames were brilliant designers. For them, design wasn't about style, it was a philosophy and a way of living and thinking. This is from a lecture by Charles Eames.

There's sort of a parable I'd like to . . . In India . . . I guess it's a parable: In India, sort of the lowest, the poorest, the, those, those without and the lowest in caste, eat very often--particularly in southern India--they eat off of a banana leaf. And those a little bit up the scale, eat off of a sort of a un . . . a low-fired ceramic dish. And a little bit higher, why, they have a glaze on--a thing they call a "tali"--they use a banana leaf and then the ceramic as a tali upon which they put all the food. And there get to be some fairly elegant glazed talis, but it graduates to--if you're up the scale a little bit more--why, a brass tali, and a bell-bronze tali is absolutely marvelous, it has a sort of a ring to it. And then things get to be a little questionable. There…

BBPlayer - A Simple HTML5 Audio Player

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BBPlayer is a minimalist HTML5 audio player for playlists that I made for a project recently. If you're looking for the best HTML5 audio player there are now many available; BBplayer provides a simple alternative with a clean and simple design that can be easily styled using CSS.



BBPlayer uses the HTML5 audio element and allows you to add multiple audio source tracks to easily create a playlist.

Visit the bbplayer demo page or get the code from github.

The Christmas Dream

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© Darren DeRidder

Improving Bayesian Filters

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Last time we looked at a Simple Introduction to Naive Bayesian Filters (or classifiers), and saw how they work using the example of a box of chocolates. It turns out there's a simple trick you can use to make Bayesian filters more effective. I haven't seen it applied before, but it seems like an obvious technique in certain situations, and I found that it improves the efficacy of filtering by up to 10% in my test cases.

Bayesian filters are used for things like spam filters, where they look for certain words and phrases and rate the "spamminess" of emails. The presence of certain words tips off the spam filter and sends spam to your junk folder. When you're filtering spam, you don't really care about the non-spammy words that an email contains, and you don't care about words that are missing. There are over 600,000 words in the English language. Most of them will not be in an email. You simply don't care about the words that aren't there, if you&…

A Simple Introduction to Naive Bayesian Filters

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In the field of data analysis and machine learning algorithms, naive Bayesian filters remain popular since they're relatively easy to implement yet surprisingly effective.  Most introductions to Bayesian filtering dive straight into mathematics, but Bayesian filters are simple enough that you can intuitively see how they work by stepping through an example.

Let's say we've got a box of chocolates, and some of them have nuts inside, and we don't like nuts. We'd like to be able to tell which chocolates have nuts in them.  The chocolates are all different shapes, sizes and colors; some are wrapped and some aren't. The only way to tell if a chocolate contains nuts is to take a bite and see. By sampling the box of chocolates and keeping track of the shape, size, color and wrapping of all the ones we tried, we could come up with a pretty good idea of which ones are most likely to have nuts.

You could make a list of characteristics: size, color, shape, and wrapping. …

Kenka Matsuri

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Participants in the Kenka Masturi (Fight Festival) carrying a shrine, Himeji, Japan


© 2012 Darren DeRidder