ReadableStream

Background

A ReadableStream is returned by the readable property inside TransformStream.

locked boolean
- A Boolean value that indicates if the readable stream is locked to a reader.

pipeTo(destinationWritableStream, optionsPipeToOptions) : Promise<void>
- Pipes the readable stream to a given writable stream destination and returns a promise that is fulfilled when the write operation succeeds or rejects it if the operation fails.
pipeThrough(transformStream, optionsPipeToOptions) : ReadableStream
- Pipes the readable stream to the writable side of a given TransformStream and returns the transform's readable side, so that calls can be chained. options accepts the same values as pipeTo().
getReader(optionsObject) : ReadableStreamDefaultReader
- Gets an instance of ReadableStreamDefaultReader and locks the ReadableStream to that reader instance. This method accepts an object argument indicating options. The only supported option is mode, which can be set to byob to create a ReadableStreamBYOBReader, as shown here:

let reader = readable.getReader({ mode: 'byob' });

cancel(reasonstringoptional) : Promise<void>
- Cancels the stream. reason is an optional human-readable string indicating the reason for cancellation. reason will be passed to the underlying source’s cancel algorithm. Any data not yet read is lost.
tee() : [ReadableStream, ReadableStream]
- Locks the stream and returns an array of two new ReadableStream instances, each of which reads the same data as the original stream. Backpressure to the underlying source follows the branch with the most unread data, which avoids unbounded buffering when one branch reads more slowly than the other, as long as the underlying source responds to backpressure. Refer to workerd's streams documentation ↗ for implementation details.
values(optionsObject) : AsyncIterableIterator
- Returns an async iterator that reads and consumes the chunks of the stream. This method accepts an object argument indicating options. The only supported option is preventCancel, which, when true, prevents the stream from being canceled when the iterator exits early (for example, from a break statement). A ReadableStream is also async iterable directly:

for await (const chunk of readable) {
	console.log(chunk);
}

for await (const chunk of readable) {
  console.log(chunk);
}

preventClose bool
- When true, closure of the source ReadableStream will not cause the destination WritableStream to be closed.
preventAbort bool
- When true, errors in the source ReadableStream will no longer abort the destination WritableStream. pipeTo will return a rejected promise with the error from the source or any error that occurred while aborting the destination.

ReadableStream.from(asyncIterable) : ReadableStream
- Creates a new ReadableStream whose chunks are the values yielded by asyncIterable, which may be any iterable or async iterable, including an async generator.

const stream = ReadableStream.from(
	(async function* () {
		yield "hello ";
		yield "world";
	})(),
);

const stream = ReadableStream.from(
  (async function* () {
    yield 'hello ';
    yield 'world';
  })()
);