1. 构造函数
2. PaymentRequestEvent
3. 属性
4. bubbles
5. cancelable
6. composed
7. currentTarget
8. defaultPrevented
9. eventPhase
10. hashCode
11. instrumentKey
12. isTrusted
13. matchingTarget
14. methodData
15. modifiers
16. path
17. paymentRequestId
18. paymentRequestOrigin
19. runtimeType
20. target
21. timeStamp
22. topLevelOrigin
23. total
24. type
25. 方法
26. composedPath
27. noSuchMethod
28. openWindow
29. preventDefault
30. respondWith
31. stopImmediatePropagation
32. stopPropagation
33. toString
34. waitUntil
35. 运算符
36. 运算符 ==