edit md

Author: Wscats

react/component/src/communication/README.md

@@ -277,4 +277,7 @@ var ChildrenComponent4_2 = React.createClass({
 });                
 ReactDOM.render(<ParentComponent4/>, document.getElementById('div4'));       
 ```
-[效果预览](https://wscats.github.io/react-tutorial/react/component/src/communication/communication.html)
+
+### 效果预览
+
+- [父子组件双向通信](https://wscats.github.io/react-tutorial/react/component/src/communication/communication.html)