1. 构造函数
2. FormData
3. 属性
4. hashCode
5. runtimeType
6. 方法
7. append
8. appendBlob
9. delete
10. get
11. getAll
12. has
13. noSuchMethod
14. set
15. toString
16. 运算符
17. operator ==
18. 静态属性
19. supported