'BMap' is not defined

I wraped my components like this 

```
componentDidMount(){
    this.map = new BMap.Map(this.id);
    this.map.centerAndZoom(new BMap.Point(121.406316,31.009703), 22);
    this.map.addControl(new BMap.MapTypeControl());   
    this.map.setCurrentCity("上海");   
    this.map.enableScrollWheelZoom(true);    
  }
```

and i use create-react-app as a boilerplate,it can not compiled
