WritableStreamDefaultWriter.desiredSize
The desiredSize read-only property of the
WritableStreamDefaultWriter interface returns the desired size required
to fill the stream's internal queue.
Value
An integer. Note that this can be negative if the queue is over-full.
The value will be null if the stream cannot be successfully written to
(due to either being errored, or having an abort queued up), and zero if the stream is
closed.
Exceptions
TypeError- : The writer's lock is released.