Summary

We opened this chapter with three closely related patterns, which are Strategy, State, and Template.

Strategy allows us to extract the common parts of a family of closely related components into a component called the context and allows us to define strategy objects that the context can use to implement specific behaviors. The State pattern is a variation of the Strategy pattern where the strategies are used to model the behavior of a component when under different states. The Template pattern, instead, can be considered the "static" version of the Strategy pattern, where the different specific behaviors are implemented as subclasses of the template class, which models the common parts of the component.

Next, we learned about what has now become a core pattern in Node.js, which is Iterator. We learned how JavaScript offers native support for the pattern (with the iterator and iterable protocols), and how async iterators can be used as an alternative to complex...