1. 构造函数
  2. BackgroundFetchedEvent
  3. 属性
  4. bubbles
  5. cancelable
  6. composed
  7. currentTarget
  8. defaultPrevented
  9. eventPhase
  10. fetches
  11. hashCode
  12. id
  13. isTrusted
  14. matchingTarget
  15. path
  16. runtimeType
  17. target
  18. timeStamp
  19. type
  20. 方法
  21. composedPath
  22. noSuchMethod
  23. preventDefault
  24. stopImmediatePropagation
  25. stopPropagation
  26. toString
  27. updateUI
  28. waitUntil
  29. 运算符
  30. 运算符 ==