我正在入侵一个Node程序,该程序使用SMTP协议捕获SMTP电子邮件并对邮件数据采取行动。库将邮件数据作为流提供,但我不知道如何将其转换为字符串。

我目前正在用stream.pipe(process. pipe)将其写入标准输出。stdout, {end: false}),但正如我所说的,我需要一个字符串中的流数据,一旦流结束,我就可以使用它。

我如何收集所有的数据从一个Node.js流到一个字符串?


当前回答

另一种方法是将流转换为promise(参考下面的示例),然后使用then(或await)将解析值分配给变量。

function streamToString (stream) {
  const chunks = [];
  return new Promise((resolve, reject) => {
    stream.on('data', (chunk) => chunks.push(Buffer.from(chunk)));
    stream.on('error', (err) => reject(err));
    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
  })
}

const result = await streamToString(stream)

其他回答

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);
})

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);
});

简单易用的流行(每周超过500万次下载)和轻量级的get-stream库:

https://www.npmjs.com/package/get-stream

const fs = require('fs');
const getStream = require('get-stream');

(async () => {
    const stream = fs.createReadStream('unicorn.txt');
    console.log(await getStream(stream)); //output is string
})();

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()));

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));
  });