ReadableStreamDefaultController: desiredSize property

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This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨January 2020⁩.

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The desiredSize read-only property of the ReadableStreamDefaultController 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.

Examples

The A readable stream with an underlying push source and backpressure support example in the spec provides a good example of using desiredSize to manually detect when the stream is full and apply backpressure, and also of using ReadableStreamDefaultController.error() to manually trigger a stream error if another part of the system it relies on fails.

Specifications

Browser compatibility

See also

• Using readable streams
• ReadableStreamDefaultController