Why JavaScript?

I started writing about machine learning (ML) in JavaScript in 2010. At the time, Node.js was brand new and JavaScript was just beginning to come into its own as a language. For much of the history of the internet, JavaScript had been seen as a toy language, used to create simple dynamic interactions on web pages.

The perception of JavaScript began to change in 2005 with the release of the Prototype JavaScript Framework, which aimed to simplify AJAX requests and help developers deal with cross-browser XMLHttpRequest. The Prototype Framework also introduced the familiar dollar function as an alias for `document.getElementById`: `$(“myId”)`, for instance.

One year later, John Resig released the wildly popular jQuery library. At the time of writing, w3techs.com reports that jQuery is used on 96% of websites whose JavaScript libraries are known to them (which accounts for 73% of all websites). jQuery worked to make common JavaScript operations cross-browser compatible and easy to achieve, bringing important tools such as AJAX requests, Document Object Model (DOM) traversal and manipulation, and animations to web developers everywhere.

Then, in 2008, the Chrome web browser and the Chrome V8 JavaScript engine were released. Chrome and V8 introduced a marked performance improvement over older browsers: JavaScript was now fast, owing in large part to the V8 engine's innovative just-in-time compiler that builds machine code directly from JavaScript.

JavaScript became more popular as jQuery and Chrome took over the web. Developers historically have never loved JavaScript as a programming language, but with jQuery in the picture, running on a fast and modern browser, it became clear that JavaScript was an underutilized tool and capable of much more than it had been used for previously.

In 2009, the JavaScript developer community decided to break JavaScript free from the web browser environment. The CommonJS initiative was launched early that year, and Node.js followed after a few months. CommonJS modules' goal was to develop a standard library and improve the ecosystem for JavaScript so that it could be used outside of the browser environment. As part of this effort, CommonJS standardized a module-loading interface that allowed developers to build libraries that they could share with others.

The release of Node.js in mid-2009 rocked the JavaScript world by giving JavaScript developers a new paradigm to consider: JavaScript as a server-side language. Packing the Chrome V8 engine under the hood made Node.js surprisingly fast, though the V8 engine doesn't deserve all of the credit for the software's performance. The Node.js instance uses an event loop to process requests, so it can handle a large number of concurrent connections despite being single-threaded.

The novelty of JavaScript on the server, its surprising performance, and the early introduction of the npm registry which let developers publish and discover modules, attracted thousands of developers. The standard library published with Node.js was primarily low-level I/O APIs, and developers raced to see who could publish the first good HTTP request wrapper, the first easy-to-use HTTP server, the first high-level image processing library, and so on. The rapid early growth of the JavaScript ecosystem generated confidence in developers who were reluctant to adopt the new technology. JavaScript, for the first time, was being seen as a real programming language, rather than just something we tolerated because of web browsers.

While JavaScript as a programming platform was maturing, the Python community was busy working on ML, in part inspired by Google's success in the market. The foundational and very popular number processing library, NumPy, was released in 2006, though it had existed in one form or another for a decade prior. A ML library called scikit-learn was released in 2010, and that was the moment I decided to start teaching ML to JavaScript developers.

The popularity of ML in Python and the ease of building and training models with tools, such as scikit-learn, astounded me and many others. In my eyes, the surge in popularity caused an ML bubble; because models were so easy to build and run, I found that many developers didn't actually understand the mechanics of the algorithms and techniques they were using. Many developers lamented their underperforming models, not understanding that they themselves were the weak link in the chain.

Machine learning at the time had been seen as mystical, magical, academic, accessible only to a select few geniuses, and only accessible to Python developers. I felt differently. Machine learning is just a category of algorithms with no magic involved. Most of the algorithms are actually easy to understand and reason about!

Rather than showing developers how to import Bayes in Python, I wanted to show developers how to build the algorithms from scratch, an important step in building intuition. I also wanted my students to largely ignore the popular Python libraries that existed at the time, because I wanted to reinforce the notion that ML algorithms can be written in any language and Python is not required.

I chose JavaScript as my teaching platform. To be perfectly honest, I chose JavaScript in part because it was considered a bad language by many at that time. My message was machine learning is easy, you can even do it in JavaScript! Fortunately for me, Node.js and JavaScript were both becoming incredibly popular, and my early articles on ML in JavaScript were read by over a million curious developers in the following years.

I also chose JavaScript in part because I didn't want ML to be seen as a tool only accessible to academics, or computer scientists, or even college graduates. I believed, and still believe, that these algorithms can be thoroughly understood by any competent developer, given enough practice and repetition. I chose JavaScript because it allowed me to reach a new audience of frontend and full-stack web developers, many of whom were self-taught or had never studied computer science formally. If the goal was to demystify and democratize the field of ML, I felt it was much better to reach the web developer community rather than the backend Python programmer community, which as a whole was already more comfortable with ML at the time.

Python has always been and remains the language of choice for ML, in part due to the maturity of the language, in part due to the maturity of the ecosystem, and in part due to the positive feedback loop of early ML efforts in Python. Recent developments in the JavaScript world, however, are making JavaScript more attractive to ML projects. I think we will see a major ML renaissance in JavaScript within a few years, especially as laptops and mobile devices become ever more powerful and JavaScript itself surges in popularity.