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Understanding React 18's New Features

• Frontend Development • HeStudy
#react #javascript #frontend

Introduction

React 18 is a major version update that introduces many exciting new features, particularly concurrent rendering capabilities.

Concurrent Rendering

Concurrent rendering is one of the most important new features in React 18. It allows React to handle multiple state updates simultaneously, improving application responsiveness.

import { startTransition } from "react";

function handleClick() {
  // Urgent update
  setInputValue(input);

  // Non-urgent update
  startTransition(() => {
    setSearchQuery(input);
  });
}

How It Works

Concurrent rendering enables React to:

  1. Pause the rendering process
  2. Prioritize urgent updates
  3. Prepare new UI in the background

Automatic Batching

React 18 extends batching functionality to automatically batch updates in Promises, setTimeout, and event handlers.

// React 18 will automatically batch these updates
setTimeout(() => {
  setCount((c) => c + 1);
  setFlag((f) => !f);
  // React will only re-render once
}, 1000);

New Hooks

useId

The useId Hook generates unique IDs, particularly useful for server-side rendering.

import { useId } from "react";

function NameFields() {
  const id = useId();
  return (
    <div>
      <label htmlFor={id + "-firstName"}>First Name</label>
      <input id={id + "-firstName"} type="text" />
    </div>
  );
}

useTransition

useTransition allows you to mark certain updates as “transitions”, preventing them from blocking the UI.

import { useTransition } from "react";

function SearchResults() {
  const [isPending, startTransition] = useTransition();
  const [query, setQuery] = useState("");

  function handleChange(e) {
    startTransition(() => {
      setQuery(e.target.value);
    });
  }

  return (
    <>
      <input onChange={handleChange} />
      {isPending && <Spinner />}
      <Results query={query} />
    </>
  );
}

useDeferredValue

useDeferredValue lets you defer updating part of the UI.

import { useDeferredValue } from "react";

function SearchPage({ query }) {
  const deferredQuery = useDeferredValue(query);

  return (
    <>
      <SearchInput query={query} />
      <Suspense fallback={<Loading />}>
        <SearchResults query={deferredQuery} />
      </Suspense>
    </>
  );
}

Suspense Improvements

React 18 has improved how Suspense works, making it more stable and powerful.

<Suspense fallback={<Loading />}>
  <LazyComponent />
</Suspense>

Migration Recommendations

To upgrade to React 18:

  1. Install the latest version: npm install react@18 react-dom@18
  2. Use the new root API: createRoot(container).render(<App />)
  3. Test your application
  4. Gradually adopt new features

Summary

The new features in React 18 make React applications smoother and more efficient. Concurrent rendering, automatic batching, and new Hooks are all important features worth learning and adopting.

References

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