While we won't discuss native code module development in this book, we do need to make sure that they can be built. Some modules in the NPM repository are native code, and they must be compiled with a C or C++ compiler to build the corresponding .node files (the .node extension is used for binary native-code modules).
The module will often describe itself as a wrapper for some other library. For example, the libxslt and libxmljs modules are wrappers around the C/C++ libraries of the same name. The module includes the C/C++ source code, and when installed, a script is automatically run to do the compilation with node-gyp.
The node-gyp tool is a cross-platform command-line tool written in Node.js for compiling native add-on modules for Node.js. We've mentioned native code modules several times, and it is this tool that compiles them for use with Node.js.
You can easily see this in action by running these commands:
$ mkdir temp
$ cd temp
$ npm install libxmljs...