[merge files by nodejs stream] #nodejs #stream #fs

merge-files.js

async function mergeFiles(output, files) {
  const outputStream = fs.createWriteStream(output, {
    encoding: 'utf8',
    flags: 'w+',
  });

  const merge = (fileToMerge) => new Promise((resolve, reject) => {
    const fileStream = fs.createReadStream(fileToMerge, { encoding: 'utf8' });
    fileStream.on('end', () => {
      fileStream.close();
      resolve(true);
    }).on('error', (e) => {
      reject(e);
    });
    fileStream.pipe(outputStream, { end: false });
  });

  for await (const file of files) {
    await merge(file);
  }
  outputStream.close();
};