ReadableStream DefaultReader
A reader is used when you want to read from a ReadableStream
, rather than piping its output to a WritableStream
.
A ReadableStreamDefaultReader
is not instantiated via its constructor. Rather, it is retrieved from a ReadableStream
:
const { readable, writable } = new TransformStream();const reader = readable.getReader();
-
reader.closed
: Promise- A promise indicating if the reader is closed. The promise is fulfilled when the reader stream closes and is rejected if there is an error in the stream.
-
read()
: Promise- A promise that returns the next available chunk of data being passed through the reader queue.
-
cancel(reasonstringoptional)
: 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 -- if this readable stream is one side of aTransformStream
, then its cancel algorithm causes the transform’s writable side to become errored withreason
.
- Cancels the stream.
-
releaseLock()
: void- Releases the lock on the readable stream. A lock cannot be released if the reader has pending read operations. A
TypeError
is thrown and the reader remains locked.
- Releases the lock on the readable stream. A lock cannot be released if the reader has pending read operations. A
Was this helpful?
- Resources
- API
- New to Cloudflare?
- Products
- Sponsorships
- Open Source
- Support
- Help Center
- System Status
- Compliance
- GDPR
- Company
- cloudflare.com
- Our team
- Careers
- 2025 Cloudflare, Inc.
- Privacy Policy
- Terms of Use
- Report Security Issues
- Trademark