For additional learning with JavaScript, I suggest you check out some of the following resources:
- Mozilla Developer Network at https://developer.mozilla.org/en-US/docs/Web/JavaScript
- Secrets of the JavaScript Ninja, John Resig, Bear Bibeault, Manning
- Learning JavaScript Design Patterns, Addy Osmani, O'Reilly
- JavaScript: The Good Parts, Douglas Crockford, O'Reilly
The Node API online documentation is going to be your best bet to fully understanding everything that's available within the Node core set of modules. The Node API docs can be found at http://nodejs.org/api.
Additionally, there is a great website that teaches Node using actual programming problems that you must solve. The emphasis with these exercises is to understand the nuts and bolts of how Node works and get down into the fundamentals of working with streams, asynchronous I/O, promises, and more. Node School can be found at http://nodeschool.io.
Finally, the creators of MongoDB offer an amazing 7-8 week online training and certification programs completely free of charge, where you will learn everything you need to be a true MongoDB master. This can be found at MongoDB University at https://university.mongodb.com.
Now it's time to dive in and start writing some real code!