Configuring Eclipse to run standalone JavaScript files (Using Node.js/Google V8 Engine)

I recently started studying JavaScript in greater detail so that I could work on some side projects of my own. My new found interest was sparked in a large part by the wonderful server-side JavaScript framework, Node.js. However, while working through the various tutorials that I had collected for the same, it became painfully evident that creating anything non-trivial in standalone JavaScript was a pain in the proper place. This is hardly surprising since the entire life-cycle of JavaScript has been primarily within the confines of the browser. However, becoming swiftly tired of embedding snippets of code within the <script> tags in HTML pages to test out various concepts of the language, I began looking for alternatives.

The first obvious choice was the excellent Firefox Scratchpad (Tools->Web Developer->Scratchpad. I am using Firefox 16.0.2, but this has been always the location of Scratchpad ever since I can remember). This is a wonderful piece of software that works for most of the scenarios while learning JavaScript, but falls short in terms of useful options such as debug options, or linking script files together in a modular fashion.

The next option that I evaluated was the eval support provided by Firebug. This is a far more advanced tool than Scratchpad, but again, when the size and complexity of the code goes beyond a certain point, it is essentially doing something that it was not designed to do.

What I really wanted in this specific case was complete IDE support for executing JavaScript projects. Ideally, I would like to use Eclipse as the IDE, with a JavaScript perspective for all the formatting and validation bits, and link an external tool to execute the script files. Getting the JavaScript perspective to work on the version of Eclipse that I am using, Juno was a breeze. The latter part – getting some suitable engine to run standalone JavaScript code, and getting it to work with Eclipse was the harder bit. Having begun tinkering with Node.js, I saw that their engine basically was a wrapper around Google’s V8 JavaScript Engine. So now I had two options: follow the elaborate set of steps listed out on that site, and generate binaries using Visual Studio (while hoping for the best), or I could simply use Node.js’s own executable wrapper! A little bit of Googling, and I found the following site – http://www.epic-ide.org/running_perl_scripts_within_eclipse/entry.htm, which made life much easier for me. The example given is for Perl, but the steps work perfectly for JavaScript as well.

Steps to configure Eclipse to work with Node.js’s JavaScript engine

1. Open the ‘External Tools’ window (Run->External Tools->External Tools Configuration)

2. In the ‘Name’ field, enter a name for the new configuration (such as ‘JavaScript_Configuration’)

3. In the ‘Location’ field, enter the path to the windows executable (C:\WINDOWS\system32\cmd.exe on my Windows 7 machine)

4. In the ‘Working Directory’ field, enter ‘C:\WINDOWS\system32’. This is because we are referring to the executable in the ‘Location’ field as ‘cmd.exe’, for which this is the working directory.

5. In the ‘Arguments’ field, we need to add the following string:

/C “cd ${container_loc} && node ${resource_name}”

Obviously, the ‘/C’ at the beginning of the line is the flag that requests the cmd.exe tool to execute the supplied string, and then terminate. The ${container_loc} field refers to the absolute path of the currently selected resource’s (JavaScript script file in this case) parent, and the ${resource_name} variable corresponds to the name of the currently selected resource (the JavaScript script file). Check out this site for more variables associated with the External Tools configuration – http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.platform.doc.user%2Fconcepts%2Fconcepts-exttools.htm.

Of course, we assume here that the “node” executable is available through Windows’ PATH environment variable.
And that’s it, we’re done! To check that everything is working as expected, I create a sample file, test.js in a new JavaScript project, which contains the following simple code snippet:

(function() {
console.log(“Hello, World!”);
})();

When we execute this file (using Run->External Tools->JavaScript_Configuration), we see that it works perfectly!

And of course, this approach can be applied to various other languages that are not supported by default by Eclipse, or for which there is no suitable Eclipse plugin available.