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The Future of UI Development: Exploring React 18's Newest Features



React 18 introduces groundbreaking updates like Concurrent Rendering, transforming how developers build and manage dynamic UIs. This blog delves into these innovations, highlighting their impact on the future of web development.

How to upgrade to React 18

Let's first see how we can upgrade to React 18

  1. Update react and react-dom to 18 Using npm
npm install react@18 react-dom@18

Using yarn

yarn add react@18 react-dom@18
  1. Modify Entry file

In index.js, update the rendering method to use the new createRoot.

React 17 (Before):

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';

ReactDOM.render(<App />, document.getElementById('root'));

React 18 (After):

import React from 'react';
import { createRoot } from 'react-dom/client';
import App from './App';

const container = document.getElementById('root');
const root = createRoot(container);
root.render(<App />);

Concept of Concurrent Rendering

Concurrent Rendering in React represents a significant shift in the way React handles rendering of components, allowing for a more efficient and smoother user experience, especially in complex applications. Here's a detailed explanation:

Non-Blocking Rendering: Traditional React rendering can block the main thread, leading to potential performance bottlenecks, especially in large or complex applications. Concurrent Rendering introduces a non-blocking approach, where React can prepare multiple versions of the UI at the same time.

Priority-Based Rendering: It allows React to interrupt a rendering process if a higher priority update comes in. This means that React can pause, resume, and even abandon renders based on the priority of updates, which is crucial for maintaining responsiveness.

How to enable concurrent Rendering in react?

Using createRoot to initialize your application puts you in a position to use concurrent features. It's the necessary first step but not sufficient in itself to make all updates concurrent. It enables your application to utilize concurrent features like Suspense for data fetching, useTransition, and useDeferredValue.

Automatic Batching

Github StackBliz Deployed Demo

In React 17 and earlier versions, automatic batching of state updates is limited to synchronous event handlers, like clicks or form submissions. This means multiple state updates within these events are batched into a single re-render. However, in asynchronous operations like setTimeout, Promises, and async/await, each state update triggers its own re-render, which can be less efficient.

React 18 improves on this by extending automatic batching to include asynchronous operations. Now, even in contexts like setTimeout or promise resolutions, multiple state updates are batched together, leading to fewer re-renders and enhanced performance. You can opt out of this behavious using flushSync.

Consider the following code, In React 18, pressing the 'Update State' button triggers only one re-render of the component, whereas in earlier versions like React 17, it would result in two re-renders.

Transition API

A "transition" in this context is an update that can be delayed without impacting the user experience negatively. The primary purpose of the Transition API is to differentiate between urgent updates, like typing in an input field, and less urgent updates, like filtering a list based on the input.

Key Benefits

  • Improved User Experience: By separating urgent updates from non-urgent ones, the Transition API ensures that the interface remains responsive and smooth.
  • Concurrent Rendering Compatibility: It works seamlessly with concurrent rendering, allowing less urgent updates to be interrupted if more urgent updates come in.
  • Control Over Rendering Priority: Developers gain more control over the rendering priority, deciding what updates should be rendered immediately and which can wait.

Suspense Enhancements

  • Concurrent Rendering Integration: React 18's suspense feature smoothly combines with concurrent rendering to enable more fluid interactions and transitions, especially when loading data. This improves user experience and lowers perceived load times.

  • Streaming Server-Side Rendering (SSR): Suspense streams HTML from the server in order to improve SSR capabilities while awaiting data. Time-to-content is accelerated by this feature, which improves initial load performance and SEO.

  • Integration with Data Fetching Libraries: The new Suspense integrates with data fetching libraries seamlessly, making it easier to handle asynchronous data flows and loading states in applications.

  • Nested Suspense Components: Better handling of nested suspense components makes it possible to create hierarchical, complex loading states that let various application components wait for resources or data on their own.

Use Cases

  • Data-Driven apps: Suspense makes asynchronous data management easier by helping to gracefully handle loading states in apps that primarily rely on fetching data.
  • code Splitting and Lazy Loading: It works with React.lazy for code splitting, rendering components only when their code is loaded, thereby optimizing performance and user experience.
  • Complex UIs with Concurrent Features: In complex UIs utilizing concurrent features like transitions and startTransition, Suspense assists in managing component rendering based on data or resource availability.

useId Hook

useId is a new hook in React 18 designed to generate unique, stable identifiers that are consistent across both server and client renders.

Generating Unique IDs for Accessibility Attributes

Many accessibility features in web development rely on IDs to associate labels and controls (like label for input fields) or to link descriptive elements using ARIA attributes (e.g., aria-labelledby, aria-describedby).

In dynamic applications, especially when components are generated on the fly, assigning unique and stable IDs to these elements can be challenging.

The useId hook simplifies this process by generating unique and consistent IDs across renders.


  • Use of useId: We use useId to generate two unique IDs: one for the input field (inputId) and one for the label (labelId).
  • Linking Label and Input: The htmlFor attribute in the <label> tag is set to the ID of the input field. This links the label to the input, which is important for screen readers and overall accessibility.
  • ARIA Attribute: Additionally, the aria-labelledby attribute in the <input> tag is set to the ID of the label. This provides an accessible name for the input field, further enhancing accessibility.

Often, elements in a UI are contextually related. For instance, a dropdown menu might have a button to open it and a list of items within it, each requiring unique but related IDs.


  • Accordion Component: This component renders multiple AccordionItem components, each representing an item in the accordion.

  • AccordionItem Component: Each item uses useId to generate a unique identifier (accordionId), which is then used to create unique IDs for the button (buttonId) and content section (contentId) of each accordion item.

  • Accessibility: The aria-expanded, aria-controls, and aria-labelledby attributes are used to enhance the accessibility of the accordion. They provide screen readers with the necessary information about the relationship between the button and the content section.

Specifying a Shared Prefix for All Generated IDs

If you render multiple independent React applications on a single page, pass identifierPrefix as an option to your createRoot or hydrateRoot calls.

useDeferredValue Hook

useDeferredValue in React 18 allows for deferring updates to a value, helping to keep the user interface responsive by delaying the rendering of non-urgent, expensive operations. It's particularly useful for maintaining fluidity in the UI during tasks like data filtering or rendering complex components, based on rapidly changing input.

useInsertionEffect Hook

useInsertionEffect is a new hook introduced in React 18, specifically designed for custom styling libraries that inject styles into the DOM. This hook allows for injecting styles before the browser performs layout and paint, thereby preventing visual inconsistencies or flickering effects.


  • useStyle Custom Hook: This custom hook demonstrates a basic idea of how useInsertionEffect might be used in a CSS-in-JS library. It creates a <style> tag and injects CSS into it.

  • Dynamic Styling: The example shows a simple dynamic styling scenario where the text color of a div changes based on the component's state.

  • useInsertionEffect Usage: The hook is used to insert and clean up styles. It ensures that styles are injected before the browser paints the screen, thus avoiding flickering or layout shifts when styles change.

useSyncExternalStore Hook

useSyncExternalStore is a React Hook that lets you subscribe to an external store.


External Store: The externalStore is a simplified version of a store that holds a value and allows subscription.

useSyncExternalStore Hook: The hook is used to subscribe to the external store. The component will re-render only when the value in the external store changes.

State and Actions: The component displays the current value from the external store and provides a button to increment this value.