1. Dart
2. dart:html
3. CacheStorage
4. has method

CacheStorage class

1. Properties
2. hashCode
3. runtimeType
4. Methods
5. delete
6. has
7. keys
8. match
9. open
10. noSuchMethod
11. toString
12. Operators
13. operator ==

Future has(String cacheName) =>
    promiseToFuture(JS("", "#.has(#)", this, cacheName));