WritableStreamDefaultWriter.ready

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The ready getter property of the WritableStreamDefaultWriter interface returns a Promise that resolves when the desired size of the stream's internal queue transitions from non-positive to positive, signaling that it is no longer applying backpressure.

Syntax

var promise = defaultWriter.ready

Value

A Promise.

Example

The following example shows two uses of the ready property. The first uses ready to ensure that the WritableStream is done writing and thus able to receive data before sending a binary chunk. The second also checks whether the the WritableStream is done writing, but this time because the writing must be finished before the writer can be closed.

function sendMessage(message, writableStream) {
  // defaultWriter is of type WritableStreamDefaultWriter
  var defaultWriter = writableStream.getWriter();
  var encoder = new TextEncoder();
  var encoded = encoder.encode(message, {stream: true});
  encoded.forEach(function(chunk) {
    // Make sure the stream and its writer are able to
    //   receive data.
    defaultWriter.ready
    .then(function() {
      defaultWriter.write(chunk)
      .then(function() {
        console.log("Chunk written to sink.);
      })
      .catch(function(err) {
        console.log("Chunk error: " + err);
      });
    });
    // Call ready again to ensure that all chunks are written
    //   before closing the writer.
    defaultWriter.ready
    .then(function() {
      defaultWriter.close()
      .then(function() {
        console.log("All chunks written");
      })
      .catch(function(err) {
        console.log("Stream error: " + err);
      });
    });  
  });
}

Specifications

Specification Status Comment
Streams
The definition of 'ready' in that specification.
Living Standard Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 59Edge Full support 16Firefox No support NoIE No support NoOpera Full support 46Safari ? WebView Android Full support 59Chrome Android Full support 59Edge Mobile Full support 16Firefox Android No support NoOpera Android Full support 46Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

Document Tags and Contributors

Contributors to this page: connorshea, FloraFauna, chrisdavidmills, abbycar, jpmedley
Last updated by: connorshea,