1. Dart
2. dart:html
3. Navigator
4. onLine property

Navigator class

1. Properties
2. appCodeName
3. appName
4. appVersion
5. budget
6. clipboard
7. connection
8. cookieEnabled
9. credentials
10. dartEnabled
11. deviceMemory
12. doNotTrack
13. geolocation
14. language
15. languages
16. maxTouchPoints
17. mediaCapabilities
18. mediaDevices
19. mediaSession
20. mimeTypes
21. nfc
22. onLine
23. permissions
24. persistentStorage
25. platform
26. presentation
27. product
28. productSub
29. serviceWorker
30. storage
31. temporaryStorage
32. userAgent
33. vendor
34. vendorSub
35. vr
36. webdriver
37. hardwareConcurrency
38. hashCode
39. runtimeType
40. Methods
41. cancelKeyboardLock
42. getBattery
43. getGamepads
44. getInstalledRelatedApps
45. getUserMedia
46. getVRDisplays
47. registerProtocolHandler
48. requestKeyboardLock
49. requestMediaKeySystemAccess
50. requestMidiAccess
51. sendBeacon
52. share
53. noSuchMethod
54. toString
55. Operators
56. operator ==

@Unstable()
bool get onLine native;