1.2 增加一个新的react组件

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import ClickCounter from './ClickCounter';
import registerServiceWorker from './registerServiceWorker';
import './index.css';

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

import React,{Component} from 'react';
class ClickCounter extends Component{
constructor(props){
super(props);
this.onClickButton = this.onClickButton.bind(this);
this.state = {count:0};
}
onClickButton(){
this.setState({count:this.state.count+1});
}

render(){
return(
<div>
<button onClick ={this.onClickButton}> Click Me</button>

<div>
Click Count:{this.state.count}
</div>
</div>
);
}
}

export default  ClickCounter;