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.
Specifies an event listener to receive
error events. These events occur when something goes wrong.
instanceOfFileHandle.onerror = funcRef;
funcRef is a function to be called when the
error event occurs.
This feature is not part of any current specification. It is no longer on track to become a standard.