Exploring React 19: New Features 🤩 and the Reasons Behind the Delayed Release😱

9 min readJul 4, 2024

React, which many developers use with enthusiasm and follow new developments eagerly, released the first beta version of React 19 on April 25 and announced that it will be released at the beginning of summer 2024.

However, as understood from new developments, the release of React 19 has been postponed. Before discussing the reason for the postponement, I would like to talk about the latest features in React 19. Afterward, I plan to explain the reason for the delay and complete my article.

Recently, I have noticed that the use of React has started to shift towards Next.js due to features such as server-side rendering. I believe that the new features and improvements coming with React 19 will address this need and are being developed to create a significantly better version.

What are the new features that will come with React 19?

1. React Compiler

React Compiler is designed to increase the performance of the react applications and simplify the development process.

It performs various optimizations and transformations to make React components more efficient.

Here is more detailed information about React Compiler:

Main Aims and Features:

a) Performance Optimizations:

Static Extraction: React Compiler avoids redoing these operations at runtime by pre-calculating the static parts of your components. This will make your app load and run faster.
Inlining: Unnecessary function calls are avoided by directly defining (inlining) frequently used small components and functions where they are called. This allows for more efficient code generation.

b) Code Transformation and Modification:

Code Transformation: React Compiler analyzes your code and creates more optimized versions. For example, it identifies frequently used patterns and structures and offers less resource-intensive alternatives.
Dead Code Elimination: It detects unused pieces of code and removes them, reducing the size of your application and reducing loading time.

c) Improved Developer Experience:

Automatic Code Splitting: React Compiler automates the splitting of large applications into smaller parts. This specifically optimizes page load time.
Advanced Error Reporting: It helps developers resolve issues faster and easier by providing more meaningful and detailed error reports.

How to work?

React Compiler, React analyses your components and follows these steps:

a) Code Analysis:

It analyzes the structure of your code and determines which parts are static and which parts change dynamically.

b) Code Optimization:

It makes your code more efficient by applying defined optimization strategies. This includes pre-processing static content and managing dynamic content more effectively.

c) Code production:

It generates the optimized code and integrates it with your original application. The generated code is more optimized in terms of both performance and size.

2. Server Components

Server Components in React allow rendering HTML on the server and sending it to the client. This approach speeds up performance and reduces page load times by using less JavaScript on the client side. Introduced in React 18 and improved in React 19, Server Components aim to make web applications faster and more efficient.

Key Features:

a) Server-side Rendering (SSR):

Server components are processed and rendered on the server side. This allows large data processing operations and heavy calculations to be done on the server, thus reducing the load on the client side.

b) Minimal JavaScript Sending to Client:

Thanks to server components, the amount of JavaScript sent to the client is reduced. By running less code on the client side, faster loading times are achieved.

c) Better SEO and First Load Time:

Server-side rendered components provide faster initial load time and better SEO performance. Since the contents of the page are rendered on the server, search engines and users can access the page faster.

d) Combined Use of Server and Client Components:

It allows client and server components to be used together in the same code base. Server components can be used inside client components and vice versa.

Advantages:

As I mentioned above there are lots of advantages like increasing performance, SEO improvement, improved user experience, and easy data management. Therefore, this improvement is quite important for React applications.

3. Actions

The “Action” feature provides an API that makes it easy to manage user actions and component states. It is specifically designed to handle user interactions (e.g. button click, form submission) in a more controlled and efficient manner. This provides significant benefits in performance improvements and debugging processes.

Basic Usage:

Action definition, usage, and performance monitoring

It is also possible to monitor user interactions with the “Action” feature. For example:

import { action } from 'react';

function MyForm() {
  const handleSubmit = action((event) => {
    event.preventDefault();
    console.log('Form submitted');
    // Submitting the form
  });

  return (
    <form onSubmit={handleSubmit}>
      <input type="text" name="name" />
      <button type="submit">Submit</button>
    </form>
  );
}

This code handles a form submission event and is wrapped with the action function. This facilitates event traceability and performance analysis.

Why Is it important?

Performance Improvement: The “Action” feature allows user interactions to be monitored and managed more effectively. This provides performance improvements, especially in large and complex applications.
Easy Debugging: User interactions become more visible and traceable, making debugging easier.
User Experience: Faster and more efficient user interactions improve the overall user experience.

4. Use

The use API allows React to more naturally and easily handle asynchronous operations while rendering. usecan be called from anywhere and is not subject to specific rules like hooks. This simplifies the management of async functions and operations.

Simple Usage:

function UserProfile({ userId }) {
const user = use(fetchUser(userId));

return (
<div>
<h1>{[user.name](http://user.name/)}</h1>
<p>{user.email}</p>
</div>
);
}

async function fetchUser(userId) {
const response = await fetch(`/api/users/${userId}`);
return await response.json();
}

In this example, the useAPI calls the fetchUser function and uses the returned promise. React suspends this component until the promise is resolved and displays a fallback UI until it is resolved.

Conditional Usage:

The useAPI is not subject to specific rules like hooks and can be called conditionally. This makes it easy to perform different asynchronous operations in different situations.

In addition, use API hooks can also handle errors that occur during asynchronous operations.

function ConditionalUserProfile({ userId }) {
  const user = userId ? use(fetchUser(userId)) : null;
  
  return user ? (
    <div>
      <h1>{user.name}</h1>
      <p>{user.email}</p>
    </div>
  ) : (
    <p>No user selected</p>
  );
}


function UserProfile({ userId }) {
  try {
    const user = use(fetchUser(userId));
    return (
      <div>
        <h1>{user.name}</h1>
        <p>{user.email}</p>
      </div>
    );
  } catch (error) {
    return <p>Error loading user data</p>;
  }
}

Lazy Initialization:

The useAPI can be used to invoke asynchronous operations during loading of components. This ensures that components invoke asynchronous operations only when necessary.

function LazyComponent() {
  const data = use(fetchData);
  
  return (
    <div>
      <h1>{data.title}</h1>
      <p>{data.content}</p>
    </div>
  );
}

Advantages:

Cleaner and Readable Code: Managing asynchronous operations directly within the component makes the code cleaner and more understandable.
Flexible Usage: The use API can be called conditionally and is not subject to specific rules, allowing for more flexible usage.
Integrated Error Handling: Error handling can be done directly within the API, making debugging and management easier.
Performance Improvements: Asynchronous operations are started only when necessary, contributing to performance improvements.

5. Advanced ref Management

What is the ref?

ref allows us to obtain direct references to DOM elements or class components. This is specifically used for DOM manipulations, third-party library integrations, and managing component states.

Traditional ref Usage

In React, refs are usually created and assigned to components with the React.createRef() or useRef() hook. Here is the traditional usage:

import React, { useRef, useEffect } from 'react';

function MyComponent() {
  const inputRef = useRef(null);

  useEffect(() => {
    inputRef.current.focus();
  }, []);

  return <input ref={inputRef} />;
}

In this example, a reference is created with useRef(), and this reference is assigned to an input element. When the component is loaded, the input gets focused automatically.

Innovations with Advanced Ref Management:

a) Using ref as Prop

You can now pass ref directly as a prop. This eliminates the need to use forwardRef.

import React, { useRef } from 'react';

function MyInput({ inputRef }) {
  return <input ref={inputRef} />;
}

function ParentComponent() {
  const inputRef = useRef(null);

  return <MyInput inputRef={inputRef} />;
}

In this example, the inputRef in ParentComponent is passed as a prop to the MyInput component and assigned directly to the input element.

b) useImperativeHandle Improvements:

useImperativeHandle, allows more flexible customization of refs.

import React, { useRef, useImperativeHandle, forwardRef } from 'react';

const CustomInput = forwardRef((props, ref) => {
  const inputRef = useRef();

  useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    },
    clear: () => {
      inputRef.current.value = '';
    }
  }));

  return <input ref={inputRef} />;
});

function ParentComponent() {
  const inputRef = useRef();
  return (
    <div>
      <CustomInput ref={inputRef} />
      <button onClick={() => inputRef.current.focus()}>Focus</button>
      <button onClick={() => inputRef.current.clear()}>Clear</button>
    </div>
  );
}

6. Advanced Metadata Management

The advanced metadata management that comes with React 19 offers significant advantages in terms of SEO and accessibility. This innovation allows setting document metadata (e.g. <title>, <meta> tags) within components. This feature is critical to increase SEO compliance and improve user experience, especially in single-page applications (SPA). Let's explain this issue in detail:

What is Metadata Management?

Metadata are HTML tags that provide information about the content of a web page. These include the page title (<title>), description (<meta name="description">), keywords (<meta name="keywords">), social media share tags, and other important information. This data is used by search engines and social media platforms to understand and index the content of the page.

Traditionally, additional libraries are often used to manage metadata in React applications. One of the most widely used libraries is react-helmet. This library enables dynamically updating metadata within React components.

import React from 'react';
import { Helmet } from 'react-helmet';

function MyComponent() {
  return (
    <div>
      <Helmet>
        <title>My Page Title</title>
        <meta name="description" content="This is a description of my page" />
      </Helmet>
      <h1>Hello, world!</h1>
    </div>
  );
}

React 19 provides a built-in solution that makes metadata management even more integrated and natural. Thanks to this feature, you can set metadata directly through components without the need for additional libraries.

import React from 'react';
import { useMetaTags } from 'react-19-meta-tags';

function BlogPost({ title, description }) {
  useMetaTags({
    title: title,
    meta: [
      { name: 'description', content: description },
      { property: 'og:title', content: title },
      { property: 'og:description', content: description },
    ],
  });

  return (
    <div>
      <h1>{title}</h1>
      <p>{description}</p>
    </div>
  );
}

export default function App() {
  const post = {
    title: 'React 19 ile Meta Veriler Yönetimi',
    description: 'React 19 ile gelen yeni meta veri yönetimi özellikleri hakkında detaylı bilgi.',
  };

  return (
    <BlogPost title={post.title} description={post.description} />
  );
}

7. Background Asset Loading

Assets such as images and scripts are loaded in the background while the user interacts with the page. This reduces startup loading times and improves the user experience. With Suspense, the lifecycle of assets is supported so that contents are displayed only when ready.

8. New and Improved Hooks

use: Manages async functions or states within the render function.
useFormStatus: Provides form status information without passing props to child components.

Purpose: To manage form states (for example, “sending” status during the form submission process) without passing props to child components.

Usage: In form components, you can check the status of the form with the useFormStatus hook and update the components accordingly.

import React from 'react';
import { useFormStatus } from 'react-19';

function SubmitButton() {
  const { isSubmitting } = useFormStatus();

  return (
    <button type="submit" disabled={isSubmitting}>
      {isSubmitting ? 'Submitting...' : 'Submit'}
    </button>
  );
}

function MyForm() {
  const handleSubmit = async (event) => {
    event.preventDefault();
    // Submitting the form
  };

  return (
    <form onSubmit={handleSubmit}>
      <input type="text" name="name" required />
      <SubmitButton />
    </form>
  );
}

export default MyForm;

useOptimistic: Simplifies managing optimistic UI updates when fetching data.

What Are the Reasons Behind the Delayed Release?

The main reason for the delay in the release of React 19 is that the changes in the new version caused performance issues on the client side. The main issue is with the “Suspense” feature, which leads to performance loss during data fetching. In React 19, components fetch data sequentially, meaning they wait for each other, which increases loading and render times. In contrast, React 18 allowed components to fetch data in parallel, resulting in faster page loads.

While focusing on server-side components (Server Components — RSC), the React team encountered performance issues on the client side. This focus slowed down many libraries commonly used on the client side. Feedback from the developer community, particularly about the “Suspense” feature, highlighted these performance issues. For example, Dominik, the developer of React Query, pointed out these issues in a tweet, showing the differences between React 18 and React 19.

In response, the React team decided to take more time to resolve these problems. They postponed the release of React 19 until they could find a good solution for the performance issues. During this time, they are working to ensure better performance on the client side. Therefore, the release of React 19 has been delayed, and the team is focused on addressing the performance issues in the new version.

Despite the delay in React 19’s release, the new features promise significant advancements once the performance issues are resolved. Developers eagerly await its release for improved efficiency and enhanced user experiences.