useDeferredValue react hook

The useDeferredValue hook in React helps improve the performance of your application by deferring updates to a value until after more urgent updates have been processed. This is particularly useful for scenarios where you want to avoid unnecessary re-renders during user interactions, like typing in a search bar.

Simple Explanation

Imagine you have a search bar that filters a large list of items as you type. Without useDeferredValue, every keystroke would trigger a re-render, which can be slow and make the UI feel sluggish. By using useDeferredValue, you can delay the filtering until the user has finished typing, making the UI more responsive.

Basic Usage

Here’s a simple example of how to use useDeferredValue:

import { useState, useDeferredValue } from 'react';

function SearchComponent({ items }) {
  const [query, setQuery] = useState('');
  const deferredQuery = useDeferredValue(query);

  const filteredItems = items.filter(item => item.includes(deferredQuery));

  return (
    <div>
      <input
        type="text"
        value={query}
        onChange={(e) => setQuery(e.target.value)}
        placeholder="Search..."
      />
      <ul>
        {filteredItems.map((item, index) => (
          <li key={index}>{item}</li>
        ))}
      </ul>
    </div>
  );
}

Examples

1. Search Bar Filtering:

   import { useState, useDeferredValue } from 'react';

   function SearchBar({ items }) {
     const [query, setQuery] = useState('');
     const deferredQuery = useDeferredValue(query);

     const filteredItems = items.filter(item => item.toLowerCase().includes(deferredQuery.toLowerCase()));

     return (
       <div>
         <input type="text" value={query} onChange={(e) => setQuery(e.target.value)} placeholder="Search..." />
         <ul>
           {filteredItems.map((item, index) => (
             <li key={index}>{item}</li>
           ))}
         </ul>
       </div>
     );
   }

2. Live Search with API Call:

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

   function LiveSearch({ apiEndpoint }) {
     const [query, setQuery] = useState('');
     const deferredQuery = useDeferredValue(query);
     const [results, setResults] = useState([]);

     useEffect(() => {
       if (deferredQuery) {
         fetch(`${apiEndpoint}?search=${deferredQuery}`)
           .then(response => response.json())
           .then(data => setResults(data));
       }
     }, [deferredQuery]);

     return (
       <div>
         <input type="text" value={query} onChange={(e) => setQuery(e.target.value)} placeholder="Search..." />
         <ul>
           {results.map((result, index) => (
             <li key={index}>{result.name}</li>
           ))}
         </ul>
       </div>
     );
   }

3. Debounced Input:

   import { useState, useDeferredValue } from 'react';

   function DebouncedInput() {
     const [input, setInput] = useState('');
     const deferredInput = useDeferredValue(input);

     return (
       <div>
         <input type="text" value={input} onChange={(e) => setInput(e.target.value)} placeholder="Type something..." />
         <p>Deferred Input: {deferredInput}</p>
       </div>
     );
   }

4. Filtering Large List:

   import { useState, useDeferredValue } from 'react';

   function LargeListFilter({ items }) {
     const [query, setQuery] = useState('');
     const deferredQuery = useDeferredValue(query);

     const filteredItems = items.filter(item => item.toLowerCase().includes(deferredQuery.toLowerCase()));

     return (
       <div>
         <input type="text" value={query} onChange={(e) => setQuery(e.target.value)} placeholder="Filter items..." />
         <ul>
           {filteredItems.map((item, index) => (
             <li key={index}>{item}</li>
           ))}
         </ul>
       </div>
     );
   }

5. Real-time Search with Loading Indicator:

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

   function RealTimeSearch({ apiEndpoint }) {
     const [query, setQuery] = useState('');
     const deferredQuery = useDeferredValue(query);
     const [results, setResults] = useState([]);
     const [loading, setLoading] = useState(false);

     useEffect(() => {
       if (deferredQuery) {
         setLoading(true);
         fetch(`${apiEndpoint}?search=${deferredQuery}`)
           .then(response => response.json())
           .then(data => {
             setResults(data);
             setLoading(false);
           });
       }
     }, [deferredQuery]);

     return (
       <div>
         <input type="text" value={query} onChange={(e) => setQuery(e.target.value)} placeholder="Search..." />
         {loading && <p>Loading...</p>}
         <ul>
           {results.map((result, index) => (
             <li key={index}>{result.name}</li>
           ))}
         </ul>
       </div>
     );
   }

Practice Exercises

1. Create a component that filters a list of items based on user input using useDeferredValue.
2. Build a search bar component that fetches data from an API and displays results using useDeferredValue.
3. Develop a component that shows a loading indicator while fetching data with useDeferredValue.
4. Implement a component that uses useDeferredValue to debounce user input and display the deferred value.
5. Create a component that filters a large list of items and displays the filtered results using useDeferredValue.

These exercises will help you get comfortable with using the useDeferredValue hook in various scenarios.