parse-json.js

export default function parseJSON() {
  return new TransformStream({
    transform(chunk, controller) {
      controller.enqueue(JSON.parse(chunk));
    }
  });
}

split-stream.js

export default function splitStream(splitOn) {
  let buffer = '';

  return new TransformStream({
    transform(chunk, controller) {
      buffer += chunk;
      const parts = buffer.split(splitOn);
      parts.slice(0, -1).forEach(part => controller.enqueue(part));
      buffer = parts[parts.length - 1];
    },
    flush(controller) {
      if (buffer) controller.enqueue(buffer);
    }
  });
}