Is JavaScript The Next App Engine Language?

written on Sunday, 21st September, 2008

As the language of the browser, JavaScript has become a kind of common denominator among web programmers. On the server it is rare compared to Java, PHP, Ruby or Python. Could this change, since Google has built an implementation of JS and an affordable yet scalable web application infrastructure?

Scripting Language of The Open Web

JavaScript was created as a scripting language for the Netscape 2.0 browser. Other than its namesake Java, it has remained in the browser since then. Web Developers know this language because they have to use it, no matter if they like it. Throughout the late 90s and well into this decade, JavaScript was mostly regarded as a toy language for silly effects and simple form checks. Due to the more recent experience with Ajax applications and the resulting thorough coverage in technical literature, the users of JavaScript have become more professional.

The Server Domain

The development on the server side has — with some notable exceptions — ignored the language JavaScript for many years. Perl was a dominant language in the early days. Then, PHP gained momentum in the fast growing developer community during the internet bubble due to its gentle learning curve, the simple integration with MySQL and the overwhelming availability of inexpensive shared hosting. You could say that in its ubiquity, PHP has mimicked JavaScript, only on the server.
Other languages and tool chains have gained momentum since then, most notably Ruby, Java and Python. They are not as affordable as PHP (except Python on the App Engine), and seem to be used mostly because of their modern MVC frameworks.

Why JavaScript Is Not Popular on The Server

JavaScript has some fundamental weaknesses that have inhibited its inception as a server side programming language:

• JavaScript, — or rather ECMAScript — has no real standard library, it is just a language. There are no tools for file or process manipulation. There are no database bindings and there is no shared memory. There is no way to open a socket.
• In the past, JavaScript Interpreters have not been known for their performance. Anyone who has seen the message A script on this page may cause Firefox to run slow. would think twice before writing an application in JavaScript.

The Helma framework tries to address the first issue by using the Rhino Interpreter, making the Java SDK available to the JavaScript programmer. The second issue is at least partially resolved as some performance intensive tasks are moved to Java. In Java 6, Rhino is even bundled with Java. Nevertheless Helma and similar integration efforts are not very popular, compared to Rails or Struts. A reason for this might be that Java for the web (the enterprise edition) is a very serious business, while the perception of JavaScript has long been ...well, the opposite of serious. The two cultures do not seem to mix well yet, as good as the technologies might blend.

Why The App Engine Loves JavaScript

When Guido van Rossum adopted Python for the Google App Engine, he had to remove lots of features because they would not work with the sandboxed, replicating environment which is the App Engine. It turns out that the limitations of JavaScript really make it an ideal candidate for the App Engine.

• JavaScript is just a language: It cannot create sockets, files or processes. App Engine does not allow for that anyway, so this is a plus!
• The language is easily sandboxed. Web Browsers have to do this all the time. This is ideal for a shared hosting environment.
• It has a no database bindings included, but a natural serialization format, JSON. This is great for the Google Data Store, because it stores objects, not table rows.
• Recently, JavaScript Interpreters (or, lets say JavaScript Machines) have become fast. There is V8 and it is fast.

It is known (at least since Guido van Rossums talk at DjangoCon 2008) that Google plans to adopt more languages for the app engine. Also, there are four primary languages that Google uses for development: Python, Java, C++ and JavaScript. Python is already available. Java is a good candidate for the App Engine, but it is not exactly lightweight certainly not shared nothing. C++ is probably the opposite of any sandboxable language.

In combination with a template engine, a free offer on the App Engine might give the already ubiquitous JavaScript language a final boost. The prospect of one language from model definition to client side computation is certainly compelling!

To encourage further speculations: With Google's V8 machine comes an embedding, process.cc, that contains code necessary to extend a hypothetical HTTP request processing application - which could be part of a web server, for example (...) (V8 Documentation).