In this chapter, you learned about Immutable.js collection side-effects in Node.js applications. We started by looking at how to read and parse input data into collection data. Then we looked at more efficient means to build large collections out of large amounts of input data.
Next, we looked at writing data from Immutable.js collections. First, you wrote simple output to files from small collections. Then, we addressed the asynchronous nature of writing larger amounts of data and how to build abstractions around this. We then chained together many streams and lazily-evaluated sequence data.
In the final chapter of this book, we'll tie up some loose ends, and put together a coherent Immutable.js architecture that you can use in more than just one application.