Note: This feature is available in Web Workers.
The locked read-only property of the ReadableStream interface returns whether or not the readable stream is locked to a reader.
A readable stream can have at most one active reader at a time, and is locked to that reader until it is released. A reader might be obtained using ReadableStream.getReader() and released using the reader's releaseLock() method.
A boolean value indicating whether or not the readable stream is locked.
const stream = new ReadableStream({
// …
});
const reader = stream.getReader();
stream.locked;
// should return true, as the stream has been locked to a readerReadableStream() constructor