<button onClick={activateLasers}> 
 Activate Lasers
</button> 

function ActionLink() { 
 function handleClick(e) {
 e.preventDefault();
 console.log('The link was clicked.');
 }

 return (
 <a href="#" rel="external nofollow" onClick={handleClick}>
  Click me
 </a>
 );
}

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

 // 这个`this`绑定是有必要的，用来让this可以在回调中被正确指向React组件的实例对象
 this.handleClick = this.handleClick.bind(this);
 }

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

 render() {
 return (
  <button onClick={this.handleClick}>
  {this.state.isToggleOn ? 'ON' : 'OFF'}
  </button>
 );
 }
}

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