When button is clicked, previous state is not updated

Question

I have this React Class component where I cannot get the Button text to change from on to off

import React from 'react';
import ReactDOM from 'react-dom';

class Toggle extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      on: true
    }
  }

  handleClick = () => {
    // todo
    this.setState((prevState) => {
      on: !prevState.on
    })
  }

  render() {
    const {
      on
    } = this.state;
    return ( <
      button onClick = {this.handleClick} >
      {
        on ? "On" : "Off"
      } < /button>
    );
  }
}

ReactDOM.render( <
  Toggle / > ,
  document.getElementById('root')
);

I thought every time the button is clicked it would it would see the previous state and it would update.

Answer 1

You are just missing some parenthesis. If you want to implicitly return an object, you must put them.

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

Check result here