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Advanced React Component Patterns

December 05, 2017


An overview of some of the patterns covered in my recently released egghead.io course (free until Friday).

I don't know that I've ever been more excited about an egghead.io course release before (having personally published over 100 videos on egghead, that's saying something...). Two of my courses will be (have now been) released as part of egghead's annual Christmas course release celebration ๐ŸŽ‰ One is The Beginner's Guide to ReactJS and the other is Advanced React Component Patterns. Combined they amount to about 2.5 hours of content. They're each 18 high-quality videos. I can't wait for you all to see them!

awesome!

I want to take this opportunity to talk about some of the patterns you'll learn in the Advanced React Component Patterns course. I hope you find it helpful and that this preview will help you be eager to give the course a look! ๐Ÿ‘€

The course starts with a single lesson where I implement a simple toggle component that manages its own state. We use, refactor, and evolve this component to each of the patterns. My hope is that by doing things this way you can quickly identify the trade-offs of the different patterns and know when each pattern would be most appropriate.

The course wraps up by refactoring the toggle component to a redux component affectionately called "Rendux." I think that you'll be blown away by the flexibility of some of these patterns to make this refactor a pretty straightforward one.

I am blown away!

Here's a high level overview of some of the patterns we cover in the course.

Compound Components

Think of compound components like the <select> and <option> elements in HTML. Apart they don't do too much, but together they allow you to create the complete experience. The way they do this is by sharing implicit state between the components. Compound components allow you to create and use components which share this state implicitly.

In these lessons I show you how to create components which allow you to show/hide the state for the component as well as choose where to render the switch. We start with using React.Children.map to provide props to the underlying components, then we switch to context to allow you to render the components at the depth you like.

An interesting example of a compound component is seapig.

glowing seapig

Higher Order Components

Higher Order Components (HOC) are functions which return a component (fun fact, the name "Higher Order Component" is a bit of a misnomer). This pattern is pretty widely popular. The most common example of a higher order component is from react-redux. It allows you to share code by encapsulating logic in a "Wrapper" component which renders a component you pass to the Higher Order Component function.

In this lesson we create a higher order component that adds the toggle component's context to the props of the component we're "enhancing." This way we can easily create custom components which have access to the toggle component's on state and the toggle helper function.

There are actually six lessons dedicated to Higher Order Components in this course. This is to give time to explain all the weird things we have to do to make unobservable the fact your components use a Higher Order Components. If you can't guess, I'm on team "Use a Render Prop" ๐Ÿ˜‰

use a render prop

That said, it's still valuable to understand this pattern as it's such a widespread pattern and can still be useful. Later on, I show you how to implement an HOC from a render prop, which leads us to our next pattern...

Render Props

This is my favorite pattern! The earliest use of this pattern in React that I'm aware of was in react-motion by Cheng Lou. In this lesson we go back to the beginning a bit and slowly refactor our original toggle implementation to the render prop pattern. Hopefully with this refactor you'll see both the power and the simplicity of the render prop pattern.

The basic idea of the pattern is that rather than have the toggle component be responsible for doing anything special in the render method, we delegate that responsibility over to the user and we give them the state and functions necessary to allow the user of the component to render what they need for their use case.

My personal favorite implementation of this pattern (and some of the following patterns) is downshift ๐ŸŽ, but I'm a little bit biased ๐Ÿ˜…

Prop Collections andย Getters

Often when using the render prop, there are elements that commonly require the same props applied for accessibility or interactivity purposes. In the toggle example that applies to what we're calling the "toggler" or the button/element that's responsible for changing the on state of our toggle component. So we can take these common props and put them into an object collection which can be applied to the element we want.

There's a problem with prop collections that has to do with composability and leaky abstractions. If my prop collection uses an onClick, that's an implementation detail, but if I want to apply an onClick to my toggle element for my own behavior as well as apply your prop collection, that's going to lead to some problems. So I show you how you can use prop (collection) getters to avoid this shortcoming.

State Initializers

This one's pretty simple and you've actually probably used this before, but I show you a handy trick or two. Here we allow you to set the initial value (similar to defaultValue in <input />) and then a nice way to expose a reset helper function to allow users of the component to reset the component to its initial state.

Controlled Components

If you've ever "controlled" an <input /> component before by using the value prop, you might be interested to know how that works and how to implement it yourself. That's what this is all about. The basic idea is that you take some state which the component manages internally (like the on state in our Toggle component) and give control over to props. That means you reference props instead of state, and call prop callbacks instead of setState. It's an interesting pattern that makes your component much more flexible: If a user of your component doesn't like how your component manages state, they can manage it themselves!

Provider

You've very likely used a component that implements the Provider pattern before. It's used by react-redux, react-router, and many other popular libraries. The idea is actually similar to some of the things we did when making the compound component work regardless of tree depth. We start by using context, then change to use react-broadcast so it works through shouldComponentUpdate.

Conclusion

Again, we wrap everything up by showing you that these patterns are powerful and flexible enough to support both the state of a single boolean as well as our entire application state with redux. I'm really excited for you to see this one ๐Ÿ˜€

I can hardly wait

I really hope that this course will help you build more useful React components. The course will hit egghead.io ๐Ÿ”œ Enjoy!

Things to not miss:

  • StackEdit is the tool I used to write this newsletter. It's a super duper awesome markdown editorย :)
  • ReactVR by the amazing Nitin Tulswani ๐Ÿ•ถ
  • chimi: Validate the JavaScript code of your Markdown files.

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Kent C. Dodds

Kent C. Dodds is a JavaScript software engineer and teacher. He's taught hundreds of thousands of people how to make the world a better place with quality software development tools and practices. He lives with his wife and four kids in Utah.