[0]这次真的崩了，2.13 用继承的话，子类在bundle.js前面，父类在后面，会报错

2.13 用继承的话，子类在bundle.js前面，父类在后面，会报错 
 
Uncaught ReferenceError: Cannot access 'BaseUI' before initialization
 子类在430行，
 class BaseUI {}
父类在393行
class HomeUI extends BaseUI {}