Send user-initiated cancel event from service worker back to streamsaver

[eschaefer]

This solved a missing piece for me, which is to stop the writeable stream if the readable stream is cancelled by the user, by dismissing the download dialog (in FF for example).

Here's how I use it:

import streamSaver from 'streamsaver';

export const magicStreamSaver = readableStream => {
  const fileStream = streamSaver.createWriteStream('assets.zip');

  return new Promise(resolve => {
    // more optimized
    if (window.WritableStream && readableStream.pipeTo) {
      readableStream.pipeTo(fileStream).then(() => {
        console.log('done writing');

        resolve();
      });
    } else {
      window.writer = fileStream.getWriter();

      const reader = readableStream.getReader();

      const pump = async () => {
        while (true) {
          const { done, value } = await reader.read(); 

          if (streamSaver.isUserAborted) {
            break;
          }

          if (done) {
            break;
          }

          window.writer.write(value);
        }

        window.writer.close();
        resolve();
      };

      pump();
    }
  });
};

[eschaefer]

Thanks for the feedback! Will make the changes as soon as possible.