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. noSuchMethod
10. open
11. toString
12. Operators
13. operator ==

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