怎样在react中创建一个事件？

var EventEmitter = require('events').EventEmitter;
class App extends Component{
constructor(props){
super(props);
}
componentDidMount(){
this.itemChange = emitter.addListener('ItemChange',(msg,data)=>console.log(msg));//注册事件
}
componentWillUnmount(){
emitter.removeListener(this.itemChange);//取消事件
}
render(){
return (

)
}
}