Book Image

Designing React Hooks the Right Way

By : Fang Jin
Book Image

Designing React Hooks the Right Way

By: Fang Jin

Overview of this book

React hook creates a unique solution for using states in function components to orchestrate UI communication. They provide you with an easy interface to write custom data management solutions with low development and maintenance costs. Understanding how Hooks are designed enables you to use them more effectively, and this book helps you to do just that. This book starts with a custom-crafted solution to reveal why Hooks are needed in the first place. You will learn about the React engine and discover how each built-in Hook can manage a persistent value by hooking into it. You will walk through the design and implementation of each hook with code so that you gain a solid understanding. Finally, you'll get to grips with each Hook's pitfalls and find out how to effectively overcome them. By the end of this React book, you'll have gained the confidence to build and write Hooks for developing functional and efficient web applications at scale.
Table of Contents (12 chapters)

Understanding the useMemo design

React provides a useMemo hook to support a value assignment through a function that can either return a new value or an old value from the previous update:

const Title = () => {
  const label = useMemo(() => {
    return "Hello World"
  }, [])

The useMemo function takes a create function as its first input argument. This function returns a new value if invoked. The second parameter is a deps dependency array, similar to deps in useEffect. In the preceding case, "Hello World" is assigned to a label variable only once after the mount.

There's no additional data structure required for useMemo other than the basic hook support, as shown in Figure 6.1:

Figure 6.1 – Data structure for useMemo

The hook's state persists between updates, and it's up to each hook function to define what (or in which format) it wants to persist. For instance...