Summary

This chapter introduced you to the conceptual foundation of Immutable.js. Immutable data is how we prevent unwanted side-effects. With Immutable.js collections, everything results in new data. This includes changing the collection somehow—these are called persistent changes. It also includes shaping the data in order to do something with it—these are called sequence transformations.

The typical Immutable.js pattern involves chaining collection method calls together—the persistent changes and sequence transformations—ending with a side-effect.

In the next chapter, we'll write some code that creates Immutable.js collections.