INP घटाना: इवेंट हैंडलर का अनुकूलन

import { useDeferredValue, useState } from 'react';

function SearchPage() {
  const [query, setQuery] = useState('');
  const deferredQuery = useDeferredValue(query); // defers re-render of slow parts

  return (
    <>
      <input value={query} onChange={e => setQuery(e.target.value)} />
      <SearchResults query={deferredQuery} /> {/* re-renders with lower priority */}
    </>
  );
}

const [isPending, startTransition] = useTransition();

function handleFilter(value) {
  setInputValue(value); // urgent — update input immediately
  startTransition(() => {
    setFilteredList(expensiveFilter(value)); // non-urgent — can be interrupted
  });
}

const worker = new Worker(new URL('./heavy-worker.js', import.meta.url));

function processData(data) {
  return new Promise(resolve => {
    worker.postMessage(data);
    worker.onmessage = e => resolve(e.data);
  });
}

// In component:
const handleClick = async () => {
  const result = await processData(largeDataset); // doesn't block main thread
  setResult(result);
};

async function processInChunks(items) {
  const CHUNK_SIZE = 100;
  for (let i = 0; i < items.length; i += CHUNK_SIZE) {
    const chunk = items.slice(i, i + CHUNK_SIZE);
    processChunk(chunk);
    await new Promise(r => setTimeout(r, 0)); // yield to browser between chunks
  }
}

async function longTask() {
  for (const item of largeList) {
    processItem(item);
    if (/* every N items */) {
      await scheduler.yield(); // let browser handle pending clicks/inputs
    }
  }
}

// Bad — forces layout recalculation on each iteration:
items.forEach(item => {
  const height = item.offsetHeight; // READ — forces layout
  item.style.height = height * 2 + 'px'; // WRITE — dirties layout
});

// Good — batch reads, then writes:
const heights = items.map(item => item.offsetHeight); // all reads
heights.forEach((h, i) => items[i].style.height = h * 2 + 'px'); // all writes

function LikeButton({ postId }) {
  const [optimistic, setOptimistic] = useOptimistic(false);

  async function handleLike() {
    setOptimistic(true);
    await likePost(postId); // async — doesn't block
  }

  return <button onClick={handleLike}>{optimistic ? 'Liked' : 'Like'}</button>;
}