#7 most askedVery commonMediumState & hooks
Avoiding unnecessary re-renders
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🏢 Asked in real interviews
No reports yet. Were you asked this? Be the first to say where.A screen feels slow because list rows re-render on every keystroke. How do you find and fix unnecessary re-renders?
🔮 Predict the output
// Shallow comparison, like React.memo
const sameProps = (a, b) => Object.keys(a).every((k) => a[k] === b[k]);
const handler = () => {};
const render1 = { title: "Hi", onPress: handler, style: { padding: 8 } };
const render2 = { title: "Hi", onPress: handler, style: { padding: 8 } };
console.log(sameProps(render1, render2));
render2.style = render1.style;
console.log(sameProps(render1, render2));
🎤 Answer it out loud, then check yourself
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Answer out loud first, then compare.
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