1. Dart
2. dart:html
3. MutationRecord
4. oldValue property

MutationRecord class

1. Properties
2. addedNodes
3. attributeName
4. attributeNamespace
5. nextSibling
6. oldValue
7. previousSibling
8. removedNodes
9. target
10. type
11. hashCode
12. runtimeType
13. Methods
14. noSuchMethod
15. toString
16. Operators
17. operator ==

String get oldValue native;