This feature is experimental. Please share your experiences so we know what to keep or change.
The up:fragment:kept event is emitted after an existing element has been kept during a render pass.
up:fragment:kept
All keep conditions have already been evaluated. The keeping can no longer be prevented. For this, use up:fragment:keep instead.
up:fragment:keep
Preserving elements
The fragment that has been kept.
The response fragment that has been discard.
The data attached to the discarded element.
