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Ali Samir
Ali Samir

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Simplifying React Hooks: useDeferredValue 💯

#react #typescript #javascript #frontend

React’s concurrent features introduced a set of powerful hooks to optimize rendering performance. One is useDeferredValue, a lesser-known but handy hook for improving UI responsiveness in high-interaction components.

In this article, we’ll explore:

  • What useDeferredValue does

  • Why and when to use it

  • How to use it with TypeScript

  • Real-world examples to illustrate its benefits

🔍 What is useDeferredValue?

useDeferredValue is a React hook that lets you defer re-rendering of a value until the browser has spare time. It was introduced in React 18 as part of the Concurrent Rendering model.

In simpler terms:

It helps keep your UI responsive by postponing the update of non-critical values.

🚀 Why Use useDeferredValue?

Imagine a scenario where a user types into a search input, and the search results list is expensive to render. Without useDeferredValue, React will re-render the list on every keystroke, possibly lagging the UI.

With useDeferredValue, you can keep the input field snappy and defer the update of the results.

🧪 Basic Syntax 

const deferredValue = useDeferredValue(value);
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  • value: The current value you want to defer.
  • deferredValue: The deferred version of the original value, which updates in a lower-priority render.

⚙️ Example with TypeScript

Let’s implement a search input with a large results list, using useDeferredValue to keep the input responsive.

✅ Before Optimization 

import React, { useState } from 'react';

const SearchComponent: React.FC = () => {
  const [query, setQuery] = useState('');

  const results = Array.from({ length: 10000 }, (_, i) => `Item ${i}`).filter(item =>
    item.toLowerCase().includes(query.toLowerCase())
  );

  return (
    <>
      <input value={query} onChange={e => setQuery(e.target.value)} />
      <ul>
        {results.map(item => (
          <li key={item}>{item}</li>
        ))}
      </ul>
    </>
  );
};
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🧠 After Optimization with useDeferredValue 

import React, { useState, useDeferredValue } from 'react';

const SearchComponent: React.FC = () => {
  const [query, setQuery] = useState<string>('');
  const deferredQuery = useDeferredValue(query);

  const results = Array.from({ length: 10000 }, (_, i) => `Item ${i}`).filter(item =>
    item.toLowerCase().includes(deferredQuery.toLowerCase())
  );

  return (
    <>
      <input value={query} onChange={e => setQuery(e.target.value)} />
      <ul>
        {results.map(item => (
          <li key={item}>{item}</li>
        ))}
      </ul>
    </>
  );
};
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✅ Benefit: The input remains responsive even if rendering 10,000+ results because React defers the filtering until there's time.

📏 TypeScript Best Practices

1. Strong Typing for State

const [query, setQuery] = useState<string>('');
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2. Use useMemo for Expensive Computations

const filteredResults = useMemo(() => {
  return allItems.filter(item => item.includes(deferredQuery));
}, [deferredQuery]);
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3. Combine with Suspense or useTransition for Better UX

const [isPending, startTransition] = useTransition();

<input
  value={query}
  onChange={(e) => {
    const value = e.target.value;
    startTransition(() => {
      setQuery(value);
    });
  }}
/>
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⚡ Real-World Use Cases

  • Search bars with large result sets

  • Live filtering in data tables

  • Real-time visualizations that need to stay responsive

  • Rich text editors or markdown previews

  • AI chat apps where rendering can be delayed while preserving fast typing

❗ Things to Keep in Mind

  • It doesn’t cancel renders—it just lowers their priority.

  • Use it to optimize rendering, not for fetching or skipping logic.

  • Combine it with useMemo, React.memo, and useTransition for best results.

🏁 Final Thoughts

React’s useDeferredValue is a game-changer when you’re dealing with large, expensive UI updates. It’s especially valuable in modern web apps that aim for seamless user experiences.

By integrating it with TypeScript and performance-focused patterns, you can create blazingly fast, delightful React apps 🚀

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Happy Coding!

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