WritableStreamDefaultWriter.desiredSize

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

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

Syntax

var desiredSize = writableStreamDefaultWriterInstance.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
Streams
The definition of 'desiredSize' in that specification.
Living Standard Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support5916 No No46 ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support595916 No46 ? ?

Document Tags and Contributors

Contributors to this page: connorshea, chrisdavidmills
Last updated by: connorshea,