结合异步迭代器实现 Node.js 流式数据复制

// 糟糕的示例，没有数据积压处理
readable.on('data', data => {
  writable.write(data)
});

function _write(dest, chunk) {
  return new Promise(resolve => {
    if (dest.write(chunk)) {
      return resolve(null);
    }

    dest.once('drain', resolve);
  })  
}

function myCopy(src, dest) {
  return new Promise(async (resolve, reject) => {
    dest.on('error', reject);

    try {
      for await (const chunk of src) {
        await _write(dest, chunk);
      }
      resolve();
    } catch (err) {
      reject(err);
    }
  });
}

const readable = fs.createReadStream('text.txt');
const writable = fs.createWriteStream('dest-text.txt');
await myCopy(readable, writable);