The ReadableStreamDefaultReader
interface of the Streams API represents a default reader that can be used to read stream data supplied from a network (e.g. a fetch request).
Constructor
ReadableStreamDefaultReader()
- Creates and returns a
ReadableStreamDefaultReader
object instance.
Properties
ReadableStreamDefaultReader.closed
Read only- Allows you to write code that responds to an end to the streaming process. Returns a promise that fulfills if the stream becomes closed or the reader's lock is released, or rejects if the stream errors.
Methods
ReadableStreamDefaultReader.cancel()
- Cancels the stream, signaling a loss of interest in the stream by a consumer. The supplied reason argument will be given to the underlying source, which may or may not use it.
ReadableStreamDefaultReader.read()
- Returns a promise providing access to the next chunk in the stream's internal queue.
ReadableStreamDefaultReader.releaseLock()
- Releases the reader's lock on the stream.
Examples
In the following example, an artifical Response
is created to stream HTML fragments fetched from another resource to the browser.
It demonstrates the usage of a ReadableStream
in combination with a Uint8Array
.
fetch("https://www.example.org/").then((response) => { const reader = response.body.getReader(); const stream = new ReadableStream({ start(controller) { // The following function handles each data chunk function push() { // "done" is a Boolean and value a "Uint8Array" return reader.read().then(({ done, value }) => { // Is there no more data to read? if (done) { // Tell the browser that we have finished sending data controller.close(); return; } // Get the data and send it to the browser via the controller controller.enqueue(value); push(); }); }; push(); } }); return new Response(stream, { headers: { "Content-Type": "text/html" } }); });
Specifications
Specification | Status | Comment |
---|---|---|
Streams The definition of 'ReadableStreamDefaultReader' in that specification. |
Living Standard | Initial definition |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
ReadableStreamDefaultReader | Chrome Full support 52 | Edge Full support ≤79 | Firefox
Full support
65
| IE ? | Opera Full support 39 | Safari ? | WebView Android Full support 52 | Chrome Android Full support 52 | Firefox Android
Full support
65
| Opera Android Full support 41 | Safari iOS ? | Samsung Internet Android Full support 6.0 |
ReadableStreamDefaultReader() constructor | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
cancel | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
closed | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
read | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
releaseLock | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
Legend
- Full support
- Full support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.
- User must explicitly enable this feature.
- User must explicitly enable this feature.