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

When using React you should generally not need to call addEventListener to add listeners to a DOM element after it is created. Instead, just provide a listener when the element is initially rendered.

Becareful about 'this':

class Toggle extends React.Component {  constructor(props) {    super(props);    this.state = {isToggleOn: true};    // This binding is necessary to make `this` work in the callback    this.handleClick = this.handleClick.bind(this);  }  handleClick() {    this.setState(prevState => ({      isToggleOn: !prevState.isToggleOn    }));  }  render() {    return (              {
    this.state.isToggleOn ? 'ON' : 'OFF'}          );  }}ReactDOM.render(  
     ,  document.getElementById('root'));

或者可以用下面的方法解决： （利用ES6箭头函数）

class LoggingButton extends React.Component {  // This syntax ensures `this` is bound within handleClick.  // Warning: this is *experimental* syntax.  handleClick = () => {    console.log('this is:', this);  }  render() {    return (              Click me          );  }}

或者

class LoggingButton extends React.Component {  handleClick() {    console.log('this is:', this);  }  render() {    // This syntax ensures `this` is bound within handleClick    return (       this.handleClick(e)}>        Click me          );  }}

 

 以上均来自于react官网docs。

 

可以在js 中用debugger来断点调试