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# 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.
