Summary

First-class functions are part and parcel of using a popular library such as React and its patterns. They also power any and every delegation of implementation, especially on built-ins such as Array. Another core tenet of functional programming is pure functions. Using pure functions for complex data manipulation logic or an abstraction layer around a data structure is a great pattern that was put forward by the popular Redux state management solution. Any side effects and/or dependencies that must be mocked make it that much harder to reason about a complex data manipulation. Higher-order functions and specific techniques such as currying and partial application are widespread in day-to-day JavaScript development. Currying and partial application is a way to design functions with an interface that makes each step of specialization "savable" since it is already a function that has already been applied with a certain number of parameters.

The composition can have...