Don't Forget React Memo

Rate this content
Bookmark

React developers intrigue us with the so-called React Forget compiler [that’s supposed to inject useMemo and useCallback into code automatically]. However, we still can't figure out best practices for useCallback, useMemo, and React.memo when we write it on our own. The worst scenario is if we continue to put it everywhere without understanding. As a result, it can bring noticeable harm to the performance of our application. In this talk, on real-life use cases, you will see solutions to the problem of using hooks wrong or overusing them!

This talk has been presented at React Summit 2022, check out the latest edition of this React Conference.

FAQ

A new compiler called React memo was discussed at React Conf 2021, which is designed to automatically inject React memo, use callback, and use memo into your code.

No, the new React memo compiler is still in developer mode and there is no specified timeline for its general availability.

The talk addressed the common issue of overusing React hooks like use memo and use callback, and a gap in understanding how these hooks work.

To create a custom hook in React, start by returning a plain JavaScript object from the hook that holds a value which can be accessed and modified persistently using useState or useRef.

The primary difference is that use memo includes an extra condition check for value changes to determine if a re-render is necessary, whereas use ref does not have this condition.

Use callback in React is equivalent to use memo but is specifically used for memoizing functions instead of values.

It is recommended to wrap child components with React Memo when using use callback in a parent component to prevent unnecessary re-renders. Also, for components dependent on props or states, wrapping them with use callback can optimize performance.

Use memo is beneficial for optimizing expensive calculations such as filtering, sorting, and formatting, with React table being a great example of its application.

Khrystyna Landvytovych
Khrystyna Landvytovych
7 min
17 Jun, 2022

Comments

Sign in or register to post your comment.

Video Summary and Transcription

The Talk covers topics such as React memo compiler, use memo and use callback, building custom hooks, and the benefits of using use ref. It also explores the similarities between use memo and use ref, and the use of React Memo for preventing re-renders and optimizing expensive calculations. The speaker also shares personal information and contact details.
Available in Español: No olvides React Memo

1. Introduction to React Memo and Custom Hooks

Short description:

I'm going to talk about the React memo compiler, the gap in understanding how use memo and use callback works, and the best practices. I will also discuss building a custom hook and the benefits of using use ref instead of use state. Finally, I will introduce my own use memo function with shallow compare.

Okay, hi, everyone. I'm so glad that you have joined me and make some little bit noise. Let's make some interactions. Where is the noise? Yeah. So, have you ever – okay. Have you already seen React Conf 2021? Please raise your hands up. Oh, so few. Okay. Just a quick look through. It has a new compiler called React memo, which is supposed to inject React memo, use callback, use memo, automatically in your code. It sounds really fascinating, but unfortunately, it's still a developer mode and I have no clue when it's going to be in the nearest future.

So, let's back up to our daily life, and I notice that there is still a gap of understanding how use memo and use callback works. We are overusing it. About what is that memorization? And the hardest question is now how can we figure it out the best practices? So, let me introduce myself. My name is Kristina. I'm software engineer at SoftSurf. And today I'm going to talk about it in details.

So, when I see such issues, I'm a mathematician person. Background, I just do simple things. I simplify it or approve it. And the best way to figure it out is just to forget use memo and to write its own custom hook. So, we are going to build hook from scratch. What we need to do? First one, we should return plain JavaScript object. Its value can be accessed and modified and we shouldn't forget about that it should be persist. I need some object instead of creating a new one of the subsequent render. So, I use it's used state for implement this thing and its return an array and index 0 is a current value. If I have started to use hooks like used state, why I cannot replace it by use ref? I can do this and it does the same thing and it's more readable. So, what another thing we should add into our function? It's updating over and over again but we don't need it. And it can help us shallow compare as does it in React. So, wrapping all our ideas, I create my own use memo function with value for current value and the previous one.

2. Exploring use Memo, use Callback, and React Memo

Short description:

I discuss the similarities between use memo and use ref, and the extra condition check in use memo. I also share my knowledge on using use callback and use memo, such as wrapping child components with React Memo to prevent re-renders and creating Howk components with dependencies. Additionally, I mention the use of use memo for optimizing expensive calculations like filtering and sorting. Lastly, I dedicate a slide to my country and provide information on how to find me on Google, Twitter, and Github.

Then I evoke shallow equals where I started checking for is it array for its length and finally I check it for their items are new for us. If everything is okay it returns true and then we override it and return a value so making like shorting something up we can modify object not only by use ref. How was interesting for me that use memo is so similar to use ref but the only difference is that it has extra condition check and there is another question comes to me that if use call back is equivalent to use memo and now it's not a secret and we can understand why.

So I hope after this talk looking at tweet or looking at react documentation it's not only words for you. It's also you have a profound knowledge by proves. Hooray.

And now I just want to take a bonus part of it and to share my knowledge how I use use callback and use memo. First one when you have parent component and child component. If in parent component you use use callback I highly recommend you to wrap child component with React Memo to prevent its re-renders. And next one is when you want to create your own Howk component with dependencies. I also recommend you to wrap it with use callback. If you don't do this, don't worry! Yes, Howk plugin will call you back. And another example of using use memo. It's quite simple for optimizing expensive calculations such as filtering, sorting, and fomenting. And the great example is React table does.

And the last slide is dedicated to my country. We still need a support. We still need some donates and ammunition. Here you can find further information and don't be afraid to ask Ukrainian any questions you have. And here, if you want to find me in Google, in Google, you just can write my nickname and you will follow to my Twitter and Github. I will be really appreciative of you if you join me.

Check out more articles and videos

We constantly think of articles and videos that might spark Git people interest / skill us up or help building a stellar career

A Guide to React Rendering Behavior
React Advanced Conference 2022React Advanced Conference 2022
25 min
A Guide to React Rendering Behavior
Top Content
This transcription provides a brief guide to React rendering behavior. It explains the process of rendering, comparing new and old elements, and the importance of pure rendering without side effects. It also covers topics such as batching and double rendering, optimizing rendering and using context and Redux in React. Overall, it offers valuable insights for developers looking to understand and optimize React rendering.
Building Better Websites with Remix
React Summit Remote Edition 2021React Summit Remote Edition 2021
33 min
Building Better Websites with Remix
Top Content
Remix is a web framework built on React Router that focuses on web fundamentals, accessibility, performance, and flexibility. It delivers real HTML and SEO benefits, and allows for automatic updating of meta tags and styles. It provides features like login functionality, session management, and error handling. Remix is a server-rendered framework that can enhance sites with JavaScript but doesn't require it for basic functionality. It aims to create quality HTML-driven documents and is flexible for use with different web technologies and stacks.
Don't Solve Problems, Eliminate Them
React Advanced Conference 2021React Advanced Conference 2021
39 min
Don't Solve Problems, Eliminate Them
Top Content
Kent C. Dodds discusses the concept of problem elimination rather than just problem-solving. He introduces the idea of a problem tree and the importance of avoiding creating solutions prematurely. Kent uses examples like Tesla's electric engine and Remix framework to illustrate the benefits of problem elimination. He emphasizes the value of trade-offs and taking the easier path, as well as the need to constantly re-evaluate and change approaches to eliminate problems.
React Compiler - Understanding Idiomatic React (React Forget)
React Advanced Conference 2023React Advanced Conference 2023
33 min
React Compiler - Understanding Idiomatic React (React Forget)
Top Content
Watch video: React Compiler - Understanding Idiomatic React (React Forget)
Joe Savona
Mofei Zhang
2 authors
The Talk discusses React Forget, a compiler built at Meta that aims to optimize client-side React development. It explores the use of memoization to improve performance and the vision of Forget to automatically determine dependencies at build time. Forget is named with an F-word pun and has the potential to optimize server builds and enable dead code elimination. The team plans to make Forget open-source and is focused on ensuring its quality before release.
Using useEffect Effectively
React Advanced Conference 2022React Advanced Conference 2022
30 min
Using useEffect Effectively
Top Content
Today's Talk explores the use of the useEffect hook in React development, covering topics such as fetching data, handling race conditions and cleanup, and optimizing performance. It also discusses the correct use of useEffect in React 18, the distinction between Activity Effects and Action Effects, and the potential misuse of useEffect. The Talk highlights the benefits of using useQuery or SWR for data fetching, the problems with using useEffect for initializing global singletons, and the use of state machines for handling effects. The speaker also recommends exploring the beta React docs and using tools like the stately.ai editor for visualizing state machines.
Routing in React 18 and Beyond
React Summit 2022React Summit 2022
20 min
Routing in React 18 and Beyond
Top Content
Routing in React 18 brings a native app-like user experience and allows applications to transition between different environments. React Router and Next.js have different approaches to routing, with React Router using component-based routing and Next.js using file system-based routing. React server components provide the primitives to address the disadvantages of multipage applications while maintaining the same user experience. Improving navigation and routing in React involves including loading UI, pre-rendering parts of the screen, and using server components for more performant experiences. Next.js and Remix are moving towards a converging solution by combining component-based routing with file system routing.

Workshops on related topic

React Performance Debugging Masterclass
React Summit 2023React Summit 2023
170 min
React Performance Debugging Masterclass
Top Content
Featured WorkshopFree
Ivan Akulov
Ivan Akulov
Ivan’s first attempts at performance debugging were chaotic. He would see a slow interaction, try a random optimization, see that it didn't help, and keep trying other optimizations until he found the right one (or gave up).
Back then, Ivan didn’t know how to use performance devtools well. He would do a recording in Chrome DevTools or React Profiler, poke around it, try clicking random things, and then close it in frustration a few minutes later. Now, Ivan knows exactly where and what to look for. And in this workshop, Ivan will teach you that too.
Here’s how this is going to work. We’ll take a slow app → debug it (using tools like Chrome DevTools, React Profiler, and why-did-you-render) → pinpoint the bottleneck → and then repeat, several times more. We won’t talk about the solutions (in 90% of the cases, it’s just the ol’ regular useMemo() or memo()). But we’ll talk about everything that comes before – and learn how to analyze any React performance problem, step by step.
(Note: This workshop is best suited for engineers who are already familiar with how useMemo() and memo() work – but want to get better at using the performance tools around React. Also, we’ll be covering interaction performance, not load speed, so you won’t hear a word about Lighthouse 🤐)
Concurrent Rendering Adventures in React 18
React Advanced Conference 2021React Advanced Conference 2021
132 min
Concurrent Rendering Adventures in React 18
Top Content
Featured WorkshopFree
Maurice de Beijer
Maurice de Beijer
With the release of React 18 we finally get the long awaited concurrent rendering. But how is that going to affect your application? What are the benefits of concurrent rendering in React? What do you need to do to switch to concurrent rendering when you upgrade to React 18? And what if you don’t want or can’t use concurrent rendering yet?

There are some behavior changes you need to be aware of! In this workshop we will cover all of those subjects and more.

Join me with your laptop in this interactive workshop. You will see how easy it is to switch to concurrent rendering in your React application. You will learn all about concurrent rendering, SuspenseList, the startTransition API and more.
React Hooks Tips Only the Pros Know
React Summit Remote Edition 2021React Summit Remote Edition 2021
177 min
React Hooks Tips Only the Pros Know
Top Content
Featured Workshop
Maurice de Beijer
Maurice de Beijer
The addition of the hooks API to React was quite a major change. Before hooks most components had to be class based. Now, with hooks, these are often much simpler functional components. Hooks can be really simple to use. Almost deceptively simple. Because there are still plenty of ways you can mess up with hooks. And it often turns out there are many ways where you can improve your components a better understanding of how each React hook can be used.You will learn all about the pros and cons of the various hooks. You will learn when to use useState() versus useReducer(). We will look at using useContext() efficiently. You will see when to use useLayoutEffect() and when useEffect() is better.
React, TypeScript, and TDD
React Advanced Conference 2021React Advanced Conference 2021
174 min
React, TypeScript, and TDD
Top Content
Featured WorkshopFree
Paul Everitt
Paul Everitt
ReactJS is wildly popular and thus wildly supported. TypeScript is increasingly popular, and thus increasingly supported.

The two together? Not as much. Given that they both change quickly, it's hard to find accurate learning materials.

React+TypeScript, with JetBrains IDEs? That three-part combination is the topic of this series. We'll show a little about a lot. Meaning, the key steps to getting productive, in the IDE, for React projects using TypeScript. Along the way we'll show test-driven development and emphasize tips-and-tricks in the IDE.
Web3 Workshop - Building Your First Dapp
React Advanced Conference 2021React Advanced Conference 2021
145 min
Web3 Workshop - Building Your First Dapp
Top Content
Featured WorkshopFree
Nader Dabit
Nader Dabit
In this workshop, you'll learn how to build your first full stack dapp on the Ethereum blockchain, reading and writing data to the network, and connecting a front end application to the contract you've deployed. By the end of the workshop, you'll understand how to set up a full stack development environment, run a local node, and interact with any smart contract using React, HardHat, and Ethers.js.
Designing Effective Tests With React Testing Library
React Summit 2023React Summit 2023
151 min
Designing Effective Tests With React Testing Library
Top Content
Featured Workshop
Josh Justice
Josh Justice
React Testing Library is a great framework for React component tests because there are a lot of questions it answers for you, so you don’t need to worry about those questions. But that doesn’t mean testing is easy. There are still a lot of questions you have to figure out for yourself: How many component tests should you write vs end-to-end tests or lower-level unit tests? How can you test a certain line of code that is tricky to test? And what in the world are you supposed to do about that persistent act() warning?
In this three-hour workshop we’ll introduce React Testing Library along with a mental model for how to think about designing your component tests. This mental model will help you see how to test each bit of logic, whether or not to mock dependencies, and will help improve the design of your components. You’ll walk away with the tools, techniques, and principles you need to implement low-cost, high-value component tests.
Table of contents- The different kinds of React application tests, and where component tests fit in- A mental model for thinking about the inputs and outputs of the components you test- Options for selecting DOM elements to verify and interact with them- The value of mocks and why they shouldn’t be avoided- The challenges with asynchrony in RTL tests and how to handle them
Prerequisites- Familiarity with building applications with React- Basic experience writing automated tests with Jest or another unit testing framework- You do not need any experience with React Testing Library- Machine setup: Node LTS, Yarn