JavaScript E4X

In previous posts, I discussed the SpiderMonkey command line shell js and how to add support to it to enable full access (read, write, create, copy, delete, etc.) to the local filesystem via the File object and the NSPR library. While rumaging around in the source code and documentation for js, I found that js partially supported the EX4 XML extension via a user configurable option. This post looks at what it takes to load an XML document into js from your local filesystem, process it and write out the resulting document to your local filesystem using File objects and

JavaScript File Object

As you are probably aware JavaScript engines such as SpiderMonkey typically do not allow access to the local filesystem for reasons of security.  To enable developers to test the scripts from a command line, js includes the load() function which enables you to load one or more JavaScript scripts into the SpiderMonkey engine.  However this is not sufficient for our purposes as no means is provided to write to the filesystem.  Looking more closely at the source code, I noticed support for File objects.  This support is not enabled by default however.  It is not sufficient to simply recompile SpiderMonkey