1. Dart
2. dart:html
3. UnderlyingSourceBase
4. cancel method

##### UnderlyingSourceBase class

1. Properties
2. hashCode
3. runtimeType
4. Methods
5. cancel
6. notifyLockAcquired
7. notifyLockReleased
8. pull
9. start
10. noSuchMethod
11. toString
12. Operators
13. operator ==

# cancel method

Future cancel (Object reason)

## Implementation

    Future cancel(Object reason) =>
        promiseToFuture(JS("", "#.cancel(#)", this, reason));