Node.js, by design, can have some limitations, notably in terms of performance. To overcome these limitations, the designers of Node.js have implemented the handling of addons, which are native software components.
See what an addon is by going to NPM, at http://www.npmjs.com/package/xppq (to which the below badge corresponds). You will find there an XML parser and preprocessor that I have developed1), as well as a link to the entire corresponding source code.
Test this addon:
npm install xppq2)), and then launching
npm explore xppq -- node test.js; you will then see the result of the parsing of an XML example file after going through the preprocessor,
Regarding the sources, you may perhaps be particularly interested by the
runkit.js files, which show some examples of use of the addon.