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