reactjs / reactjs/react.dev

How to understand that components might do an extra re-rendering when arrow function callback is passed to lower components

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Description

Refering to the doc of handling-events

class LoggingButton extends React.Component {
  handleClick() {
    console.log('this is:', this);
  }

  render() {
    // This syntax ensures `this` is bound within handleClick
    return (
      <button onClick={() => this.handleClick()}>
        Click me
      </button>
    );
  }
}

The problem with this syntax is that a different callback is created each time the LoggingButton renders. In most cases, this is fine. However, if this callback is passed as a prop to lower components, those components might do an extra re-rendering. We generally recommend binding in the constructor or using the class fields syntax, to avoid this sort of performance problem.

I got confused
Could anyone provide a demo what shows the difference of the 3 patterns [bind/ public class fields syntax/ arrow function] in rendering

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the handling-events documentation linked in the issue and review the section describing callback creation during rendering. Add a clear demo or explanation comparing constructor binding, public class fields, and arrow-function callbacks passed to lower components, showing when an extra render occurs. Done means the performance difference and recommended pattern are understandable from the documentation.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, react
Domain
documentation
Issue type
Documentation
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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