javascript - componentWillReceiveProps, componentDidUpdate for React Hook

Question

I run into two challenges:

• Even if, as per React guideline, derived state is discouraged, but some edge cases still need it.
  In terms of a functional component with React Hook, What is the equivalent implementation with React Hook, If I do need derived state ? which in class component, will be updated in componentWillReceiveProps on every parent render

see below code sample:

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      count: props.count > 100 ? 100 : props.count,
    }

  }

  /*What is the equivalent implementation when React Hook is used here componentWillReceiveProps*/
  componentWillReceiveProps(nextProps) {
    if (nextProps.count !== this.props.count) {
      this.setState({
        count: nextProps.count > 100 ? 100 : nextProps.count
      });
    }
  }

  render() {
    return ( <
      div > {
        this.state.count
      } <
      /div>
    );
  }
}

export default App;

question from:https://stackoverflow.com/questions/54843675/componentwillreceiveprops-componentdidupdate-for-react-hook

Answer 1

The react hook equivalent to the old componentWillReceive props can be done using the useEffect hook, just specifying the prop that we want to listen for changes in the dependency array.

I.e:

export default (props) => {

    useEffect( () => {
        console.log('counter updated');
    }, [props.counter])

    return <div>Hi {props.counter}</div>
}

For componentDidUpdate just by omitting the dependency array, the useEffect function will be called after every re-render.

I.e:

export default (props) => {

    useEffect( () => {
        console.log('counter updated');
    })

    return <div>Hi {props.counter}</div>
}