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Last updated on Aug 20, 2024
Last updated on Apr 13, 2024
Hello there, React enthusiasts!
Brace yourself for an exhilarating journey as we unravel the mysteries of React Concurrent Mode. This powerful new feature, introduced in React 18, is set to revolutionize the way we build user interfaces. It's like stepping into a new dimension where your React apps can work on multiple tasks at once, without blocking the main thread.
Imagine a world where your app can remain responsive even during heavy computations or network requests. A world where the UI doesn't freeze when the user interacts with it. That's the promise of the Concurrent feature. It's not just a new feature, it's a whole new way of thinking about React.
So, buckle up, and let's dive into the world of concurrency in React!
In the realm of React, concurrent rendering is a game-changer. It's a new way of rendering that helps your app stay responsive under heavy load and gives you more control over how updates get scheduled.
But what does it mean, really?
In a nutshell, concurrent rendering enables React to work on multiple tasks at once without blocking the main thread. This is a stark contrast to the traditional, synchronous rendering model where React would block the main thread until it finished rendering the component tree.
Concurrent rendering is all about creating a fluid user experience. It allows React to interrupt an ongoing rendering process to handle more urgent tasks, like responding to user input. This way, even if your app is in the middle of a large rendering task, it can still respond immediately to user interactions.
Here's a simple example to illustrate this:
1 import {unstable_createRoot} from 'react-dom'; 2 3 const root = unstable_createRoot(document.getElementById('root')); 4 5 root.render(<App />); 6
In this code snippet, we're using the unstable_createRoot function from react-dom to create a root node. This function enables concurrent rendering for the entire app.
The beauty of concurrent rendering is that it allows React to prepare multiple versions of the UI in memory and then quickly switch between them depending on user interactions and network conditions. This leads to a more responsive and fluid user experience, especially for complex apps with heavy computations or network requests.
However, concurrent rendering is not a silver bullet. It introduces a new level of complexity and requires a different way of thinking about how your app updates and renders. But once you get the hang of it, you'll see how it can take your React apps to the next level.
With the advent of React 18, the React team introduced a new concurrent renderer, which is fundamentally different from the synchronous renderer used in React 16 and previous versions. So, what exactly has changed?
In React 16, rendering was always synchronous. This means that once React started rendering a component tree, it wouldn't stop until the entire tree was rendered. This could lead to problems if a large rendering task was blocking the main thread, causing the UI to freeze and become unresponsive.
React 18, on the other hand, introduces concurrent rendering. This new mode enables React to interrupt a rendering process to handle more urgent tasks, like responding to user input. It's like having a superpower that allows React to be in multiple places at the same time.
Here's an example to illustrate the difference:
1 // React 16 2 ReactDOM.render(<App />, document.getElementById('root')); 3 4 // React 18 5 const root = ReactDOM.createRoot(document.getElementById('root')); 6 root.render(<App />); 7
In React 16, we use ReactDOM.render to render our app. In React 18, we use ReactDOM.createRoot to create a root node and then call render on that root node. This enables concurrent rendering for the entire app.
But the differences go beyond just the way we render our app. With concurrent mode, React 18 introduces a host of new features like automatic batching of multiple state updates, streaming server rendering, and React Suspense, which allows you to create a smooth loading state for your components.
In essence, concurrent mode in React 18 is a paradigm shift that changes how we think about rendering in React. It's not just about making your app faster, but also about making it more responsive and user-friendly.
React 18 is packed with a plethora of concurrent features that are designed to make your apps more responsive and user-friendly. Let's dive deep into some of these features and see how they can enhance your React apps.
1. Automatic Batching:
In previous versions of React, state updates that were triggered outside of React events were not batched together. This could lead to unnecessary re-renders and a less efficient app. React 18 introduces automatic batching, which batches multiple state updates together, resulting in a single re-render.
Here's an example:
1 const [count, setCount] = useState(0); 2 3 // In React 16, these would cause two re-renders 4 setCount(count + 1); 5 setCount(count + 1); 6 7 // In React 18, these are batched together and cause a single re-render 8
2. Streaming Server Rendering:
React 18 introduces new server rendering APIs that allow you to stream HTML from the server to the client. This means that the browser can start rendering the HTML as soon as it receives the first chunk of data, without waiting for the entire response. This can significantly improve the perceived load time of your app.
3. React Suspense:
React Suspense is a new feature in React 18 that allows you to create a smooth loading state for your components. With Suspense, you can "wait" for some code to load and declaratively specify a loading state. This can be particularly useful when dealing with code splitting or data fetching.
1 <Suspense fallback={<div>Loading...</div>}> 2 <MyComponent /> 3 </Suspense> 4
In this example, the <Suspense> component wraps around MyComponent. If MyComponent is not ready yet (maybe it's still fetching data or loading a code split chunk), React will show the fallback prop, which in this case is a simple "Loading..." div.
These are just a few of the concurrent features in React 18. There's also startTransition, which allows you to mark certain updates as "transitions" and give them a lower priority, and useDeferredValue, which allows you to defer slower state updates until faster ones have finished.
Together, these concurrent features enable React to handle complex rendering tasks more efficiently and provide a smoother, more responsive user experience.
Now that we've explored the world of concurrent rendering and its features, let's get our hands dirty and see how we can enable concurrent mode in a React app.
Step 1: Upgrade to React 18
The first step is to upgrade your app to React 18. You can do this by running the following command in your terminal:
1 npm install react@18 react-dom@18 2
Step 2: Enable Strict Mode
Next, you'll want to enable Strict Mode in your app. This will help you catch potential issues in your app that could be problematic in concurrent mode.
1 import React, { StrictMode } from 'react'; 2 3 <StrictMode> 4 <App /> 5 </StrictMode> 6
Step 3: Enable Concurrent Mode
Now, it's time to enable concurrent mode. Instead of using ReactDOM.render, you'll use ReactDOM.createRoot.
1 import { createRoot } from 'react-dom'; 2 3 const root = createRoot(document.getElementById('root')); 4 root.render(<App />); 5
And voila! You've enabled concurrent mode in your React app. Now, your app can take full advantage of the concurrent features in React 18, like automatic batching, streaming server rendering, and React Suspense.
Remember, concurrent mode is a powerful tool, but with great power comes great responsibility. It introduces a new level of complexity and requires a different way of thinking about how your app updates and renders. But once you get the hang of it, you'll see how it can take your React apps to the next level.
Now that we've covered the theory and setup of concurrent mode, let's take a look at some real-world examples of how concurrent React can be used to enhance the user experience.
Example 1: Prioritizing User Input
One of the key benefits of concurrent mode is the ability to prioritize certain tasks over others. Let's say you have a search bar in your app. As the user types into the search bar, the app filters a list of items based on the user's input.
In a traditional synchronous rendering model, if the list of items is large, filtering the list could block the main thread and cause the input to lag behind the user's typing. This can lead to a frustrating user experience.
With concurrent mode, React can interrupt the filtering process to handle the user's input, ensuring that the input stays responsive at all times.
Example 2: Smooth Loading States with Suspense
Another powerful feature of concurrent mode is React Suspense, which allows you to create smooth loading states for your components.
Let's say you have a component that fetches data from an API. In a traditional model, you would have to manage the loading state manually, which can lead to a janky user experience if not done correctly.
With Suspense, you can declaratively specify a loading state and let React handle the rest. This can lead to a much smoother user experience, as React can "wait" for the data to load and show a loading state in the meantime.
1 <Suspense fallback={<div>Loading...</div>}> 2 <DataFetchingComponent /> 3 </Suspense> 4
In this example, if DataFetchingComponent is still fetching data, React will show the fallback prop, which in this case is a simple "Loading..." div.
These are just a few examples of how concurrent React can be used to enhance the user experience. The possibilities are endless, and I'm excited to see what you'll build with these powerful new features!
React 18's concurrent mode is a game-changer for handling concurrency in your applications. It introduces a new concurrent renderer that can work on multiple tasks at once, without blocking the main thread. This is a significant improvement over the previous synchronous renderer, which could only work on one task at a time.
But how does React handle concurrency? The secret lies in the way React schedules updates. In concurrent mode, React can interrupt an ongoing rendering process to handle more urgent tasks, like responding to user input. This ensures that your app remains responsive at all times, even during heavy computations or network requests.
Here's an example to illustrate this:
1 import { startTransition } from 'react'; 2 3 function MyComponent() { 4 const [state, setState] = useState(initialState); 5 6 function handleClick() { 7 startTransition(() => { 8 setState(newState); 9 }); 10 } 11 12 // ... 13 } 14
In this example, we're using the startTransition function to mark a state update as a "transition". This tells React that this update is non urgent one and can be interrupted if there are more urgent tasks to handle.
This ability to prioritize tasks is what makes concurrent mode so powerful. It allows React to handle complex rendering tasks more efficiently and provide a smoother, more responsive user experience.
But remember, with great power comes great responsibility. Concurrent mode introduces a new level of complexity and requires a different way of thinking about how your app updates and renders. So, make sure you understand the concepts thoroughly before diving in.
One of the most intriguing aspects of React 18's concurrent mode is the so-called "double render" phenomenon. If you've been experimenting with React 18, you might have noticed that some components seem to render twice, even though they should only render once. What's going on here?
The double render is actually a feature, not a bug. It's a result of how the new concurrent renderer works. In concurrent mode, React prepares the new screen (or the updated state of a component) in memory before it updates the DOM. This is known as "rendering in memory" or "offscreen rendering".
During this phase, React might render some components one or more times, even if they don't end up being visible to the user. This is what leads to the "double render". However, these extra renders are usually fast and don't block the main thread, so they don't affect the performance of your app.
Here's an example to illustrate this:
1 function MyComponent() { 2 const [state, setState] = useState(initialState); 3 4 console.log('Render'); 5 6 // ... 7 } 8
In this example, if you run this component in concurrent mode, you might see "Render" logged twice in the console, even though the component only updates once. This is the "double render" in action.
So, don't be alarmed if you see your components rendering twice in concurrent mode. It's just React doing its thing, preparing the new screen in memory to provide a smoother user experience.
If you've been following the development of React, you might have come across the term "React Experimental". But what does it mean, and how does it relate to concurrent mode?
"React Experimental" is a term used by the React team to refer to experimental builds of React that include features that are not yet available in stable releases. These experimental builds are a way for the React team to test new features, gather feedback from the community, and iterate on their design before they are included in a stable release.
Concurrent mode was first introduced in React Experimental. It was a radical new feature that required extensive testing and feedback before it could be included in a stable release. By releasing it in React Experimental first, the React team was able to gather valuable feedback from the community and make necessary adjustments to the design and implementation of concurrent mode.
So, if you're eager to try out the latest and greatest features of React before they are officially released, keep an eye on React Experimental. But remember, features in React Experimental are subject to change and should not be used in production.
And if you're wondering how you can contribute to the development of React, trying out React Experimental and providing feedback to the React team is a great way to start. Your feedback can help shape the future of React and make it even better for everyone.
React is a living, breathing project. It's continuously being developed and improved by the React team and the open-source community. And with the release of React 18, it's clear that the future of React is bright and full of exciting possibilities.
One of the most exciting aspects of React's ongoing development is the focus on concurrency. With the introduction of concurrent mode in React 18, React has taken a big step towards a more responsive and user-friendly future. But this is just the beginning. The React team is already working on new concurrent features and improvements that will take the power of concurrent rendering to the next level.
Another exciting area of development is server components. This is a new type of component that can be rendered on the server and sent to the client as HTML. Server components can access server-side data directly, without the need for an API layer. This can significantly simplify the data fetching logic in your app and improve its performance.
And let's not forget about React Suspense, a powerful new feature that allows you to create smooth loading states for your components. Suspense is already available in React 18, but the React team is working on further improvements and new APIs that will make it even more powerful and flexible.
So, as a React developer, there's a lot to look forward to. The future of React is full of exciting new features and improvements that will make our apps more responsive, user-friendly, and fun to build. And I, for one, can't wait to see what the React team has in store for us!
React has taken the world of frontend development by storm. Since its release by Facebook in 2013, it has gained immense popularity among developers and has become one of the most widely used JavaScript libraries for building user interfaces. But why is React so popular?
One of the main reasons is its simplicity and flexibility. React is based on components, which are reusable pieces of code that can be combined to build complex user interfaces. This component-based architecture makes it easy to build and maintain large applications.
Another reason is its performance. React uses a virtual DOM and a diffing algorithm to minimize the number of updates to the actual DOM, which can be slow. This makes React applications fast and responsive, even for large applications with complex UIs.
The introduction of concurrent mode in React 18 takes this performance to the next level. By allowing React to work on multiple tasks at once and prioritize them based on their urgency, concurrent mode makes React applications even more responsive and user-friendly.
But perhaps the most important reason for React's popularity is its vibrant community. With millions of developers around the world using React, you're never alone. Whether you're looking for help with a problem, a library to simplify your development, or just some inspiration, the React community has got you covered.
And with the introduction of new features like concurrent mode, server components, and React Suspense, it's clear that React is not resting on its laurels. It's continuously evolving and improving, making it an exciting and rewarding choice for developers.
React Suspense is one of the most exciting features introduced in React 18. It provides a declarative way to handle loading states in your components, making it easier to create smooth and responsive loading experiences. But is it ready for production use?
The answer is yes, but with a caveat. While React Suspense is included in React 18 and can be used in production, it's still considered an experimental feature. This means that while it's generally stable and reliable, there may still be some edge cases and bugs that the React team is working to iron out.
One of the key things to keep in mind when using Suspense is that it requires a different way of thinking about loading states. Instead of manually managing loading states in your components, Suspense allows you to declaratively specify a loading state and let React handle the rest.
While this can simplify your code and make your loading states more consistent, it can also require some refactoring of your existing code. So, if you're planning to use Suspense in a large, existing codebase, be prepared for some work.
In conclusion, while React Suspense is a powerful tool for creating smooth loading states, it's still an experimental feature and may require some work to integrate into your existing code. But if you're starting a new project or are willing to put in the work to refactor your existing code, it can be a game-changer for your loading experiences.
With every major release of a library or framework, there's always the concern of breaking changes. React 18 is no exception. While the React team has made a concerted effort to ensure backward compatibility, there are a few changes that could potentially break your existing code.
One of the most significant changes in React 18 is the introduction of concurrent mode. While concurrent mode brings a host of benefits, it also introduces a new way of thinking about rendering and state updates in React. This could potentially break assumptions made in your existing code.
For instance, in concurrent mode, React may render components more than once, even if they don't end up being visible to the user. This is a departure from the synchronous rendering model of previous versions of React, where components were rendered exactly once.
Another potential breaking change is the introduction of automatic batching. In React 18, multiple state updates are batched together, resulting in a single re-render. This could potentially break your existing code if it relies on state updates causing immediate re-renders.
So, how can you handle these breaking changes? Here are a few tips:
Remember, while breaking changes can be challenging, they're also an opportunity to improve your code and learn more about React. So, embrace the challenge and happy coding!
As we've journeyed through the landscape of React 18 and its concurrent mode, we've seen how it introduces a new way of thinking about rendering in React. It's not just about making your app faster, but also about making it more responsive and user-friendly. The power of concurrent features in React 18 cannot be overstated.
Automatic Batching: This feature allows multiple state updates to be batched together, resulting in a single re-render. This can significantly improve the performance of your app, especially for apps with frequent state updates.
Streaming Server Rendering: This feature allows you to stream HTML from the server to the client, improving the perceived load time of your app. The browser can start rendering the HTML as soon as it receives the first chunk of data, without waiting for the entire response.
React Suspense: This feature provides a declarative way to handle loading states in your components. With Suspense, you can "wait" for some code to load and declaratively specify a loading state. This can simplify your code and provide a smoother loading experience for your users.
StartTransition: This feature allows you to mark certain updates as "transitions" and give them a lower priority. This can be useful for updates that are not urgent and can be interrupted if there are more urgent tasks to handle.
UseDeferredValue: This feature allows you to defer slower state updates until faster ones have finished. This can be useful for keeping your UI responsive during heavy computations or network requests.
These concurrent features are the heart of React 18. They provide new tools and techniques for building responsive, user-friendly apps. But remember, with great power comes great responsibility. These features introduce a new level of complexity and require a different way of thinking about how your app updates and renders. So, make sure you understand these concepts thoroughly before diving in.
We've come a long way in our exploration of React concurrent mode. From understanding the basics of concurrent rendering to diving deep into the new features of React 18, we've seen how concurrent mode is set to revolutionize the way we build user interfaces.
Concurrent mode is not just a new feature, it's a whole new way of thinking about React. It allows React to work on multiple tasks at once, without blocking the main thread. It introduces powerful new features like automatic batching, streaming server rendering, and React Suspense. And it changes how we think about rendering and state updates in React.
But with these new powers come new challenges. Concurrent mode introduces a new level of complexity and requires a different way of thinking about how your app updates and renders. It requires you to rethink your assumptions and refactor your code. And it requires you to keep learning and growing as a React developer.
But that's the beauty of React. It's a living, breathing project that's continuously evolving and improving. It's a community of millions of developers who are passionate about building better user interfaces. And it's a journey of learning, growth, and discovery.
So, as we look to the future of React with concurrent mode, I'm excited to see what you'll build. I'm excited to see how you'll use these new powers to create more responsive, user-friendly apps. And I'm excited to continue this journey with you.
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