Web/API/WritableStreamDefaultWriter/desiredSize

Draft This page is not complete.

This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.

The desiredSize read-only property of the WritableStreamDefaultWriter interface returns the desired size required to fill the stream's internal queue.

Syntax

var desiredSize = writableStreamDefaultWriter.desiredSize;

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

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	Status	Comment
StreamsThe definition of 'desiredSize' in that specification.	Living Standard	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`desiredSize` Experimental'	Chrome Full support 59	Edge Full support 16	Firefox No support No	IE No support No	Opera Full support 46	Safari ?	WebView Android Full support 59	Chrome Android Full support 59	Firefox Android No support No	Opera Android Full support 43	Safari iOS ?	Samsung Internet Android Full support 7.0

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.

WritableStreamDefaultWriter.desiredSize by Mozilla Contributors is licensed under CC-BY-SA 2.5.