prevstate react code example

Example 1: react prevstate

handleClick() {
  this.setState(prevState => ({
    isToggleOn: !prevState.isToggleOn
  }));
}

Example 2: componentDidUpdate

componentDidUpdate(prevProps, prevState) {
  if (prevState.pokemons !== this.state.pokemons) {
    console.log('pokemons state has changed.')
  }
}

Example 3: prevstate in usestate

const [prevState, setState] = React.useState([]);

setState(prevState => [...prevState, 'somedata'] );

Example 4: this.setstate prevstate

this.setState(prevState => ({ n: !prevState.n }))

Example 5: prev props

componentDidUpdate(prevProps) {
  // Utilisation classique (pensez bien à comparer les props) :
  if (this.props.userID !== prevProps.userID) {
    this.fetchData(this.props.userID);
  }
}

Example 6: prevstate in react

handleClick() {
        this.setState(prevState => {
            return {
                count: prevState.count + 1
            }
        })
    }