The limits and costs of memoizing components.
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reactperformancememoization
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memo skips re-render on stable props
Run Playgroundimport { useState, memo, useRef } from 'react';
const Child = memo(function Child({ label }) {
const renders = useRef(0);
renders.current++;
return <p>{label} child rendered <b>{renders.current}</b> time(s)</p>;
});
export default function App() {
const [count, setCount] = useState(0);
return (
<div style={{ fontFamily: 'sans-serif', padding: 24 }}>
<p>Parent count: {count}</p>
<button onClick={() => setCount((c) => c + 1)}>Re-render parent</button>
<Child label="Memoized" />
<p style={{ color: '#666' }}>Its prop is stable, so the memoized child does NOT re-render when the parent updates.</p>
</div>
);
}05
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