Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
instanceOfFileHandle.onabort = funcRef;
funcRef is a function to be called when the
abort event occurs.
This feature is not part of any current specification. It is no longer on track to become a standard.