WritableStreamDefaultWriter: desiredSize property

Note: This feature is available in Web Workers.

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.

Examples

js
const writableStream = new WritableStream(
  {
    write(chunk) {
      // ...
    },
    close() {
      // ...
    },
    abort(err) {
      // ...
    },
  },
  queuingStrategy,
);

// ...

const writer = writableStream.getWriter();

// ...

// return stream's desired size
let size = writer.desiredSize;

Specifications

Specification
Streams Standard
# ref-for-default-writer-desired-size⑥

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
desiredSize

Legend

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Full support
Full support