ReadableStreamDefaultReader
Background
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();
Properties
-
closedPromise- 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.
Methods
-
read()Promise- A promise that returns the next available chunk of data being passed through the reader queue.
-
cancel(reasonstring)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 a [TransformStream](/workers/runtime-apis/streams/transformstream/), then its cancel algorithm causes the transform’s writable side to become errored with `reason`. <aside class="DocsMarkdown--aside" role="note" data-type="warning">WarningAny data not yet read is lost. -
releaseLock()void- Releases the lock on the readable stream. A lock cannot be released if the reader has pending read operations. A
TypeErroris 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