prevent re render in child component in react js

Question

I have a counter app. I need to prevent re-render component. I want to execute Childcompnent only when I clicking on update, but here it is executing both time when I click count or update.

import { useCallback, useMemo, useState } from "react";

export const App = () => {
  const [count, setCount] = useState(0);
  const [updatecount, setUpdateCount] = useState(0);

  const incCount = () => {
    setCount(parseInt(count) + 1);
  };

  const updCount = useCallback(() => {
    return setUpdateCount(parseInt(updatecount) + 1);
  }, [updatecount]);

  return (
    <>
      <button onClick={incCount}>count</button>
      <button onClick={updCount}>update</button>
      <Childcompnent count={count} />
      <p>{updatecount}</p>
    </>
  );

};

export default App;

export function Childcompnent({ count }) {
  console.log("pressed");
  return <p>{count}</p>;
}

You're not using ChildComponent in your parent component. Why don't you want it to re-render? Here's some documentation on how to create a React snippet. Perhaps you could update your question using those steps. — Andy
– Andy, Commented Aug 27, 2022 at 12:00
Why would you not want to re-render? Please clarify and make sure this isn't an xy problem — user5734311
– user5734311, Commented Aug 27, 2022 at 12:04
means i want to execute childcomponent only when i clicking on update , but here it is executing both time when i click count,update — Saketh Elite
– Saketh Elite, Commented Aug 27, 2022 at 12:08
Apologies to the user who edited the question and who I called out. I hadn't realised that the <pre> tags were screwing up the formatting. Your edit was fine. — Andy
– Andy, Commented Aug 27, 2022 at 12:13

Sanket Shah · Accepted Answer · 2022-08-27 12:14:54Z

1

Wrap your Childcompnent in React.memo:

const Childcompnent = React.memo(({ count }) => {
  console.log("pressed");
  return <p>{count}</p>;
});

Here is the sandbox:

answered Aug 27, 2022 at 12:14

Sanket Shah

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2 Comments

Saketh Elite Over a year ago

Yeah i got the solution . is any other means can i get the same output by using useCallback method?

Sanket Shah Over a year ago

No. React.memo is used to wrap React Function components to prevent unnecessary re-renderings. The useCallback is used to memoize functions.

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