React.memo
import { useState, memo } from "react";
function areEqual(prevProps, nextProps) {
return prevProps.x === nextProps.x;
}
const Foo = memo(({ x, y }) => {
console.log("Foo", x, y);
return <div>Foo</div>;
});
const Boo = memo(({ x, y }) => {
console.log("Boo", x, y);
return <div>Boo</div>;
}, areEqual);
function App() {
console.log("App");
const [count, setCount] = useState(0);
return (
<div className="App">
<p>
<button type="button" onClick={() => setCount((count) => count + 1)}>
count is: {count}
</button>
</p>
<Foo />
<Foo x={count} />
<Foo x={new Date()} />
<Foo x={999} y={new Date()} />
<Boo x={count} />
<Boo x={new Date()} />
<Boo x={999} y={new Date()} />
</div>
);
}
export default App;
