问题太短了 我没太理解，我就按照我自己的想法和你说一下

如果不用piping的话，你需要监听你stream的data和end事件
下面是将一个文件的读流，转成buffer，然后写到别的文件里面去

const readStream = fs.createReadStream(path.join(__dirname, 'xxx.txt'))
const buffers = [];
readStream.on('data', function(buffer) {
  buffers.push(buffer);
});
readStream.on('end', function() {
  const data = Buffer.from(buffers);
  //...do your stuff...

  // such as write to file:
  fs.writeFile('xxx.txt', data, function(err) {
    // handle error, return response, etc...
  });
});
readStream.on('error', function(error){
  console.error('readStream error:', error.message);
})

不过最好推荐使用pip方式，这样如果读的buffer很大的话，对内存会有压力，pip不会

const readStream = fs.createReadStream(path.join(__dirname, './xxx_read.json'))
const writeStream = fs.createWriteStream(path.join(__dirname, './xxx_write.json'))
readStream.pipe(writeStream)
readStream.on('error', (error) => {
  console.log('readStream error', error.message);
})
writeStream.on('error', (error) => {
  console.log('writeStream error', error.message);
})