Frequently Asked Questions

React Memo: Concepts & Usage

What is React Memo?

React Memo is a higher-order component in React that memoizes the rendered output of a component. It prevents unnecessary re-renderings when the props passed to the child component remain unchanged, thereby improving application performance by reusing the last rendered result. Learn more.

How does React Memo improve performance?

React Memo enhances performance by memoizing component output and skipping re-renders when props are unchanged. This is especially useful for medium to large components that render frequently with the same props, reducing unnecessary computations and improving responsiveness. See examples.

When should I use React Memo?

Use React Memo when your component is medium to large, renders often, and frequently receives the same props. It is not recommended for very small or simple components, or when the component's state or props change frequently. Memo is a performance optimization and should not be relied upon for component logic. Read more.

How do I use React Memo in my code?

You can use React Memo by wrapping your component with memo(). For example: const MyComponent = memo((props) => { /* ... */ });. You can also provide a custom comparison function as the second argument to control when the component should re-render. See code samples.

What is memoization and how does it relate to React Memo?

Memoization is a caching technique that stores the results of expensive function calls and returns the cached result when the same inputs occur again. React Memo applies memoization to component rendering, ensuring that components only re-render when their props change. Learn more.

Can I use a custom comparison function with React Memo?

Yes, React Memo allows you to provide a custom comparison function as the second argument to memo(). This function determines whether the component should re-render by comparing previous and next props. See example.

What is the impact of React Memo on child components?

React Memo ensures that child components only re-render if their state or the props passed to them change. This reduces unnecessary renders and improves overall application performance. Read more.

Hygraph Product Information

What is Hygraph?

Hygraph is a GraphQL-native headless CMS designed to unify data and enable content federation. It empowers businesses to create impactful digital experiences by removing traditional content management pain points and offering scalability, flexibility, and efficient data querying. Learn more.

What are the key capabilities and benefits of Hygraph?

Hygraph offers GraphQL-native architecture, content federation, scalability, and rapid content delivery performance. Benefits include faster speed-to-market, control at scale, lower total cost of ownership, and improved user experience. See features.

What integrations does Hygraph support?

Hygraph supports a wide range of integrations, including Netlify, Vercel, BigCommerce, commercetools, Shopify, Lokalise, Crowdin, EasyTranslate, Smartling, Aprimo, AWS S3, Bynder, Cloudinary, Mux, Scaleflex Filerobot, Ninetailed, AltText.ai, Adminix, and Plasmic. See full list.

Does Hygraph provide an API?

Yes, Hygraph provides a powerful GraphQL API for efficient content fetching and management. API Reference.

Where can I find Hygraph technical documentation?

Comprehensive technical documentation is available at Hygraph Documentation, covering everything needed to build and deploy projects.

Pricing & Plans

What is Hygraph's pricing model?

Hygraph offers a free forever Hobby plan, a Growth plan starting at $199/month, and custom Enterprise plans. For details, visit the pricing page.

Security & Compliance

What security and compliance certifications does Hygraph have?

Hygraph is SOC 2 Type 2 compliant, ISO 27001 certified, and GDPR compliant, ensuring enterprise-grade security and regulatory compliance. See security features.

How does Hygraph protect sensitive data?

Hygraph provides SSO integrations, audit logs, encryption at rest and in transit, and sandbox environments to protect sensitive data and meet regulatory standards. Learn more.

Features & Capabilities

How does Hygraph optimize content delivery performance?

Hygraph ensures rapid content distribution and responsiveness, reducing bounce rates and increasing conversions. Optimized performance directly impacts user experience, engagement, and search engine rankings. Read more.

What feedback have customers given about Hygraph's ease of use?

Customers praise Hygraph for its intuitive interface and ease of use, noting that even non-technical users can start using it right away. The UI is described as logical and user-friendly, making it accessible for both technical and non-technical teams.

Use Cases & Benefits

Who can benefit from using Hygraph?

Hygraph is ideal for developers, IT decision-makers, content creators, project/program managers, agencies, solution partners, and technology partners. Companies that benefit most include modern software companies, enterprises seeking to modernize technologies, and brands aiming to scale across geographies or improve development velocity.

What industries are represented in Hygraph's case studies?

Hygraph's case studies span industries such as Food and Beverage (Dr. Oetker), Consumer Electronics (Samsung), Automotive (AutoWeb), Healthcare (Vision Healthcare), Travel and Hospitality (HolidayCheck), Media and Publishing, eCommerce, SaaS (Bellhop), Marketplace, Education Technology, and Wellness and Fitness. See case studies.

Can you share specific customer success stories using Hygraph?

Yes. Komax achieved a 3X faster time to market, Autoweb saw a 20% increase in website monetization, Samsung improved customer engagement with a scalable platform, and Dr. Oetker enhanced their digital experience using MACH architecture. Explore more success stories.

How long does it take to implement Hygraph and how easy is it to start?

Hygraph is designed for quick implementation. For example, Top Villas launched a new project in just 2 months from the initial touchpoint. Customers can get started quickly by signing up for a free account and using resources like documentation and onboarding guides. Get started.

What business impact can customers expect from using Hygraph?

Customers can expect time-saving through streamlined workflows, ease of use, faster speed-to-market, and enhanced customer experience through consistent and scalable content delivery. These benefits help businesses modernize their tech stack and achieve operational efficiency.

Pain Points & Solutions

What problems does Hygraph solve?

Hygraph addresses operational pains (reliance on developers for content updates, outdated tech stacks, conflicting needs from global teams, clunky user experiences), financial pains (high operational costs, slow speed-to-market, expensive maintenance, scalability challenges), and technical pains (boilerplate code, overwhelming queries, evolving schemas, cache problems, OpenID integration challenges). See product details.

How does Hygraph solve these pain points?

Hygraph provides an intuitive interface for non-technical users, modernizes legacy systems with GraphQL-native architecture, ensures consistent branding via content federation, streamlines workflows to reduce costs, accelerates project delivery, minimizes maintenance expenses, supports scalability, and simplifies development with reduced boilerplate code and streamlined query management.

What KPIs and metrics are associated with the pain points Hygraph solves?

Key metrics include time saved on content updates, system uptime, consistency in content across regions, user satisfaction scores, reduction in operational costs, time to market, maintenance costs, scalability metrics, and performance during peak usage. See CMS KPIs.

Do the pain points solved by Hygraph differ by persona?

Yes. Developers benefit from reduced boilerplate code and streamlined queries; content creators and project managers gain independence from developers and a user-friendly interface; business stakeholders see lower operational costs, easier scalability, and faster speed-to-market. See persona solutions.

Support & Implementation

What customer service and support does Hygraph offer?

Hygraph provides 24/7 support via chat, email, and phone. Enterprise customers receive dedicated onboarding and expert guidance. All users have access to documentation, video tutorials, and a community Slack channel. Contact support.

What training and technical support is available to help customers get started?

Hygraph offers onboarding sessions for enterprise customers, training resources such as video tutorials, documentation, webinars, and access to Customer Success Managers for expert guidance. Learn more.

How does Hygraph handle maintenance, upgrades, and troubleshooting?

Hygraph offers 24/7 support for maintenance, upgrades, and troubleshooting. Enterprise customers receive dedicated onboarding and expert guidance, and all users can access documentation and the community Slack channel for additional support.

Competition & Comparison

Why choose Hygraph over alternatives in the market?

Hygraph stands out with its GraphQL-native architecture, content federation, scalability, and rapid content delivery. It enables impactful digital experiences while reducing costs and improving efficiency. See product comparison.

Customer Proof & Case Studies

Who are some of Hygraph's customers?

Hygraph is trusted by companies such as Sennheiser, HolidayCheck, Ancestry, Samsung, Dr. Oetker, Epic Games, Bandai Namco, Gamescom, Leo Vegas, and Clayton Homes. See customer stories.

Blog & Content Modeling

Where can I find the Hygraph blog?

The Hygraph Blog provides the latest updates, developer tutorials, and essential guides to content modeling. Visit the Blog section on the Hygraph website.

What kind of content can I find in the Hygraph Blog?

The blog includes developer tutorials, latest updates, and essential guides to content modeling, as well as news and insights about releases and industry trends.

Who are the authors of the React Memo blog post?

The React Memo blog post was written by Aagam Vadecha and Joel Olawanle. See post.

When was the React Memo blog post written?

The React Memo blog post was last updated by Aagam on September 3, 2024, and originally written by Joel.

Webinar Event: How to Avoid Personalization Tech Traps

What is React memo and how to use it?

In this article, you will learn what React Memo means, what it does, how it works, and when or when not to use it. You will also learn how it works with detailed examples and codes.
Aagam Vadecha

Last updated by Aagam 

Sep 03, 2024

Originally written by Joel

React memo

One of the benefits of using React is its improved performance, which allows your web applications to load faster and allows you to navigate from one page to another without waiting a lot. There are scenarios where we can further improve React’s native performance, and in this article, we will see how to use Memo to improve performance.

React Memo allows us to memoize our component code and avoid unnecessary re-renders when the same props are passed to our components, thereby enhancing the performance of our React application.

What is Memoization?

Memoization is a form of caching used to store results of expensive functions and avoid repeated calls, leading to repetitive computation of results.

#What is React Memo?

Components in React are designed to re-render whenever the state or props value changes. Also, when a parent component re-renders, so do all of its child components. This can impact our application performance because, even if the change is only intended to affect the parent component, all child components attached to the parent component will be re-rendered. Ideally, child components should only re-render if their state or the props passed to them change.

React Memo is a higher-order component that wraps around a component to memoize the rendered output and avoid unnecessary renderings in cases where the props passed to the child component are the same. This improves performance because it memoizes the result and skips rendering to reuse the last rendered result.

There are two ways to use memo() :

We can wrap the actual component directly using memo:

import { memo } from "react";
const myComponent = memo((props) => {
/* component code */
});
export default myComponent;

Another option is to create a new variable to store the memoized component and then export the new variable:

import { memo } from "react";
const myComponent = (props) => {
/* render using props */
};
export const MemoizedComponent = memo(myComponent);

In the example above, myComponent outputs the same content as MemoizedComponent, but the difference between both is that MemoizedComponent’s render is memoized. This means that this component will only re-render when the props change.

Pro Tip

Important: A memoized component will not re-render when if the same props are passed to it.

#How to use React Memo

Let us understand React Memo with a Todo List example. We have a simple React-Typescript index.tsx component here.

index.tsx

import { useState } from "react";
import { ITodo } from "./types";
import Todo from "./Todo";
export function App() {
console.log("App component rendered");
const [todo, setTodo] = useState<ITodo[]>([
{ id: 1, title: "Read Book" },
{ id: 2, title: "Fix Bug" },
]);
const [text, setText] = useState("");
const addTodo = () => {
const lastId = todo[todo.length - 1].id;
let newTodo = { id: lastId + 1, title: text };
setTodo([...todo, newTodo]);
setText("");
};
return (
<div>
<input
type="text"
value={text}
onChange={(e) => setText(e.target.value)}
/>
<button type="button" onClick={addTodo}>
Add todo
</button>
<Todo list={todo} />
</div>
);
}
export default Memo;

types.ts

export interface ITodo {
id: number;
title: string;
}

In the component above, we are using state to hold all the todo items in an array, there is an input for adding a new todo to the array. Notice that at the beginning of the component, a console.log() statement will be executed when our component is rendered. The Todo component is a child component of the App component and we are passing the todo item list as a prop to it.

Todo.tsx

import { memo } from "react";
import { ITodo } from "./types";
import TodoItem from "./TodoItem";
interface TodoProps {
list: ITodo[];
}
const Todo = ({ list }: TodoProps) => {
console.log("Todo component rendered");
return (
<ul>
{list.map((item) => (
<TodoItem key={item.id} item={item} />
))}
</ul>
);
};
export default Todo;

In the code above, a console.log() statement will log a text to show when the Todo component renders. The Todo component receives the todo item list, iterates over it, and passes each todo item as a prop further to a TodoItem component.

TodoItem.tsx

import { memo } from "react";
import { ITodo } from "./types";
interface TodoItemProps {
item: ITodo;
}
const TodoItem = ({ item }: TodoItemProps) => {
console.log("TodoItem component rendered");
return <li>{item.title}</li>;
};
export default TodoItem;

The TodoItem component above also has a console.log statement to help us understand when it renders. When we run our application and check the console, we can notice that all three components render.

image1.png

We see four logs, one for the parent component (App.js), one for the Todo component, and finally, the TodoItem component renders twice because the initial todo list contains two elements. This is normal for the initial render.

Now, when we change something in the parent component that doesn’t affect the child components, only the parent component should be re-rendered. For example, when we type anything in the text field, the state of App component changes and it re-renders. This leads to unnecessary renders of the child Todo and TodoList components, even though typing in the App component should not affect the children components.

Optimizing components with React Memo

Let us now memoize some of the children components so that they only render when there is a change in props. The first component that would be memoized is the Todo component. It is important to stop re-renders whenever a user types in the text field.

We can do this by wrapping the Todo component with memo()

Todo.tsx

// Memoized Todo component
import { memo } from "react";
import { ITodo } from "./types";
import TodoItem from "./TodoItem";
interface TodoProps {
list: ITodo[];
}
const Todo = memo(({ list }: TodoProps) => {
console.log("Todo component rendered");
return (
<ul>
{list.map((item) => (
<TodoItem key={item.id} item={item} />
))}
</ul>
);
});
export default Todo;

Now that the Todo component is memoized, only the App component will re-render whenever its state changes. The Todo component will only re-render when the list prop passed to it changes. Let us now take this a step further to avoid unnecessary re-rendering whenever an item is added to the todo array.

When the todo state changes, it affects the list prop, and all existing TodoItem components on the screen will render for each item added. We want a situation where only the new item added be rendered not the existing ones. We can achieve this by memoizing the TodoItem component:

TodoItem.tsx

// Memoized TodoItem component
import { memo } from "react";
import { ITodo } from "./types";
interface TodoItemProps {
item: ITodo;
}
const TodoItem = memo(({ item }: TodoItemProps) => {
console.log("TodoItem component rendered");
return <li>{item.title}</li>;
});
export default TodoItem;

How to use custom comparison function with React Memo

React Memo makes a shallow comparison and might not function as you wish in some scenarios. If we want to have control over the comparison, we can provide a custom comparison function as the second argument.

For example, if we are passing an object containing user details as a prop to a Profile component:

index.tsx

import { useState } from "react";
import { IUser } from "./types";
const App = () => {
console.log("App rendered");
const [text, setText] = useState("");
let user: IUser = { name: "John Doe", age: 23, username: "johndoe" };
return (
<div>
<input
type="text"
value={text}
onChange={(e) => setText(e.target.value)}
/>
<Profile user={user} />
</div>
);
};

types.tsx

export interface IUser {
name: string;
age: number;
username: string;
}

Profile.tsx

import { memo } from "react";
import { IUser } from "./types";
interface ProfileProps {
user: IUser;
}
const Profile = memo(({ user }: ProfileProps) => {
console.log("Profile rendered");
return (
<div>
<p>{user.name}</p>
<p>{user.age}</p>
<p>{user.username}</p>
</div>
);
});
export default Profile;

The memoized Profile component will always render even when the user object does not change. Ideally, in this case, we should use useMemo in the parent component to fix the object passed to the Profile component. However, to understand a custom comparison function, we will implement that approach for now.

React Memo doesn't work because it only performs a shallow comparison of the component's properties. Every time the app is updated, the user variable is re-declared. We can use the second argument of the memo and provide a custom comparison function.

Profile.tsx

import { memo } from "react";
import { IUser } from "./types";
interface ProfileProps {
user: IUser;
}
const arePropsEqual = (prevProps: ProfileProps, nextProps: ProfileProps) => {
if (prevProps.user.name === nextProps.user.name) {
return true; // props are equal
}
return false; // props are not equal -> update the component
};
const Profile = memo(({ user }: ProfileProps) => {
console.log("Profile rendered");
return (
<div>
<p>{user.name}</p>
<p>{user.age}</p>
<p>{user.username}</p>
</div>
);
}, arePropsEqual);
export default Profile;

#When to use React Memo

We now understand what it means to memoize a component and the advantages of optimization. This doesn’t mean that we should memoize all our components to ensure maximum performance optimization of performance 🙃.

It is important to know when and where to memoize your component else it will not fulfill its purpose.

For example, React Memo is used to avoid unnecessary re-renders due to the same props being passed but if the state and content of your component will ALWAYS change, React Memo becomes useless.

Also, when we need to remember the values of a function or an object, we should hooks like useMemo() and useCallback().

Here are points when we should consider using memo:

  • The component is medium to big size (contains a decent amount of UI elements) to have props equality check, not very simple and small. We don’t want to optimize where optimization is more costly than re-rendering.
  • Component renders quite often.
  • Component renders with the same props often and its state/context doesn’t change quite often.

Finally, please note that memo is just a performance optimization. We should NOT rely on it for our component logic to work properly.

#Wrapping Up

In this article, we have understood what React Memo is and its usage, why, and when to use React Memo. We have also learned that using React Memo correctly prevents unnecessary re-renderings when the next props are equal to the previous ones.

Have fun coding!

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