iterable-to-readable-stream.mjs

import {ReadableStream} from 'node:stream/web';

/**
 * @param iterable an iterable (asynchronous or synchronous)
 * 
 * @see https://streams.spec.whatwg.org/#example-rs-pull
 */
 function iterableToReadableStream(iterable) {
  return new ReadableStream({
    async start() {
      if (typeof iterable[Symbol.asyncIterator] === 'function') {
        this.iterator = iterable[Symbol.asyncIterator]();
      } else if (typeof iterable[Symbol.iterator] === 'function') {
        this.iterator = iterable[Symbol.iterator]();
      } else {
        throw new Error('Not an iterable: ' + iterable);
      }
    },

    async pull(controller) {
      if (this.iterator === null) return;
      const {value, done} = await this.iterator.next();
      if (done) {
        this.iterator = null;
        controller.close();
        return;
      }
      controller.enqueue(value);
    },
  });
}


async function* createAsyncIterable() {
  yield 'how';
  yield 'are';
  yield 'you';
}
const stream1 = iterableToReadableStream(createAsyncIterable());
for await (const chunk of stream1) {
  console.log(chunk);
}

const syncIterable = ['hello', 'everyone'];
const stream2 = iterableToReadableStream(syncIterable);
for await (const chunk of stream2) {
  console.log(chunk);
}