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up.fragment up.fragment.etag(element)
JavaScript function

This feature is experimental. It may be changed or removed in a future version.

Returns the ETag of the content in the given element.

The ETag corresponds to the ETag header in the response that rendered the fragment. Alternatively the [up-etag] attribute of the element or an ancestor is used.

When the fragment is reloaded, its ETag is sent as an If-None-Match request header. The server may check the header and decide to skip rendering. See Conditional requests for a full example.


element Element

Return value


The fragment's ETag.

Return undefined if the fragment was rendered without an ETag.