whatwg-streams-impl/t.js

WHATWG Streams Implementation for Node.JS

const {ReadableStream} = require('./lib/index');

const src = [1, 2, 3, 4, 5, 6, 7, 8];

const nodeReadableStream = new require('stream').Readable({
  read() {
    if (src.length > 0) {
      this.push(String(src.shift()));
    } else {
      this.push(null);
    }
  }
});

/*
const stream = new ReadableStream({
  start(controller) {
    console.log('underlyingSource.start() called.');
  },
  pull(controller) {
    console.log('underlyingSource.pull() called.');
    if (src.length > 0) {
      controller.enqueue(src.shift());
    } else {
      controller.close();
    }
  },
  cancel(reason) {
    console.log('underlyingSource.cancel() called. Reason:', reason);
  }
});
*/

const stream = new ReadableStream({
  start(controller) {
    nodeReadableStream.pause();
    nodeReadableStream.on('data', (chunk) => {
      controller.enqueue(chunk);
      nodeReadableStream.pause();
    });
    nodeReadableStream.once('end', () => controller.close());
    nodeReadableStream.once('error', (e) => controller.error(e));
  },
  pull(controller) {
    nodeReadableStream.resume();
  },
  cancel() {
    nodeReadableStream.destroy();
  }
});

const reader = stream.getReader();

async function read() {
  let value;
  let done = false;

  while (!done) {
    ({value, done} = await reader.read());

    console.log('Read:', value, done);
    // Do something with value, if `done` is still not `true`
  }

  // Finished reading. Do something
  console.log('finished');
}

async function run() {
  await read();
  console.log('all done');
  console.log(reader);
}

run();