1. Dart
2. dart:html
3. MouseEvent
4. relatedTarget property

MouseEvent class

1. Constructors
2. MouseEvent
3. Properties
4. altKey
5. button
6. buttons
7. client
8. ctrlKey
9. dataTransfer
10. fromElement
11. layer
12. metaKey
13. movement
14. offset
15. page
16. region
17. relatedTarget
18. screen
19. shiftKey
20. toElement
21. bubbles
22. cancelable
23. composed
24. currentTarget
25. defaultPrevented
26. detail
27. eventPhase
28. hashCode
29. isTrusted
30. matchingTarget
31. path
32. runtimeType
33. sourceCapabilities
34. target
35. timeStamp
36. type
37. view
38. Methods
39. getModifierState
40. composedPath
41. noSuchMethod
42. preventDefault
43. stopImmediatePropagation
44. stopPropagation
45. toString
46. Operators
47. operator ==

EventTarget get relatedTarget =>
    _convertNativeToDart_EventTarget(this._get_relatedTarget);