In this chapter, we looked at change detection with Immutable.js collections. The main objective with change detection is avoiding side-effects when the data is the same as it was the last time the side-effect ran. We looked at using strict equality to compare collections. This works because mutative methods return the same reference when nothing has changed. Using strict equality as the mechanism for change detection can have a dramatic impact on overall application performance. For any other collection comparisons, you want to use deep equality with the equals() method.
We then implemented change detection that avoided running side-effects when the input collections didn't change from the first time the side-effect ran. We turned this into a generic function that can produce functions that have built-in side-effect caching abilities.
In the next chapter, you'll learn about sets—collections with unique values.