1. Dart
2. dart:html
3. Node
4. isConnected property

Node class

1. Properties
2. baseUri
3. childNodes
4. firstChild
5. hashCode
6. isConnected
7. lastChild
8. nextNode
9. nodeName
10. nodes
11. nodeType
12. nodeValue
13. on
14. ownerDocument
15. parent
16. parentNode
17. previousNode
18. runtimeType
19. text
20. Methods
21. addEventListener
22. append
23. clone
24. contains
25. dispatchEvent
26. getRootNode
27. hasChildNodes
28. insertAllBefore
29. insertBefore
30. noSuchMethod
31. remove
32. removeEventListener
33. replaceWith
34. toString
35. Operators
36. operator ==
37. Constants
38. ATTRIBUTE_NODE
39. CDATA_SECTION_NODE
40. COMMENT_NODE
41. DOCUMENT_FRAGMENT_NODE
42. DOCUMENT_NODE
43. DOCUMENT_TYPE_NODE
44. ELEMENT_NODE
45. ENTITY_NODE
46. ENTITY_REFERENCE_NODE
47. NOTATION_NODE
48. PROCESSING_INSTRUCTION_NODE
49. TEXT_NODE

bool get isConnected native;