ReadableStreamBYOBReader: cancel() method

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Note: This feature is available in Web Workers.

The cancel() method of the ReadableStreamBYOBReader interface returns a Promise that resolves when the stream is canceled. Calling this method signals a loss of interest in the stream by a consumer.

Note: If the reader is active, the cancel() method behaves the same as that for the associated stream (ReadableStream.cancel()).

Syntax

cancel()
cancel(reason)

Parameters

reason Optional: A human-readable reason for the cancellation. The underlying source may or may not use it.

Return value

A Promise, which fulfills with the value given in the reason parameter.

Exceptions

TypeError: The source object is not a ReadableStreamBYOBReader, or the stream has no owner.

Examples

This example code calls the cancel() method when a button is pressed, passing the string "user choice" as a reason. The promise resolves when cancellation completes.

button.addEventListener("click", () => {
  reader.cancel("user choice").then(() => console.log(`cancel complete`));
});

Note that this code can be seen running in the Using readable byte streams example code (press the Cancel stream button).

Specifications

Specification
Streams Standard # ref-for-generic-reader-cancel②

Browser compatibility

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