流没有简单的. tostring()函数(我理解)，也没有类似于. tostringasync (cb)函数(我不理解)的东西。

所以我创建了自己的helper函数:

var streamToString = function(stream, callback) {
  var str = '';
  stream.on('data', function(chunk) {
    str += chunk;
  });
  stream.on('end', function() {
    callback(str);
  });
}

// how to use:
streamToString(myStream, function(myStr) {
  console.log(myStr);
});

这对我来说是有效的，并且基于Node v6.7.0文档:

let output = '';
stream.on('readable', function() {
    let read = stream.read();
    if (read !== null) {
        // New stream data is available
        output += read.toString();
    } else {
        // Stream is now finished when read is null.
        // You can callback here e.g.:
        callback(null, output);
    }
});

stream.on('error', function(err) {
  callback(err, null);
})

以上这些方法对我都没用。我需要使用Buffer对象:

  const chunks = [];

  readStream.on("data", function (chunk) {
    chunks.push(chunk);
  });

  // Send the buffer or you can put it into a var
  readStream.on("end", function () {
    res.send(Buffer.concat(chunks));
  });

使用非常流行的stream-buffers包，你可能已经在你的项目依赖项中有了这个包，这是非常简单的:

// imports
const { WritableStreamBuffer } = require('stream-buffers');
const { promisify } = require('util');
const { createReadStream } = require('fs');
const pipeline = promisify(require('stream').pipeline);

// sample stream
let stream = createReadStream('/etc/hosts');

// pipeline the stream into a buffer, and print the contents when done
let buf = new WritableStreamBuffer();
pipeline(stream, buf).then(() => console.log(buf.getContents().toString()));

在我的例子中，响应头的内容类型是content - type: text/plain。所以，我已经从Buffer读取了数据:

let data = [];
stream.on('data', (chunk) => {
 console.log(Buffer.from(chunk).toString())
 data.push(Buffer.from(chunk).toString())
});

我通常使用这个简单的函数将流转换为字符串:

function streamToString(stream, cb) {
  const chunks = [];
  stream.on('data', (chunk) => {
    chunks.push(chunk.toString());
  });
  stream.on('end', () => {
    cb(chunks.join(''));
  });
}

使用的例子:

let stream = fs.createReadStream('./myFile.foo');
streamToString(stream, (data) => {
  console.log(data);  // data is now my string variable
});