JAVASCRIPT

prevstate in usestate

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

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

react prevstate

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

prevstate in react

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

this.setstate prevstate

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