How do I read the contents of a Node.js stream into a string variable?

javascript node.js stream
obrienmd picture obrienmd · May 16, 2012 · Viewed 127.6k times · Source

I'm hacking on a Node program that uses smtp-protocol to capture SMTP emails and act on the mail data. The library provides the mail data as a stream, and I don't know how to get that into a string.

I'm currently writing it to stdout with stream.pipe(process.stdout, { end: false }), but as I said, I need the stream data in a string instead, which I can use once the stream has ended.

How do I collect all the data from a Node.js stream into a string?

Answer

Marlon Bernardes picture Marlon Bernardes · Mar 22, 2018

Another way would be to convert the stream to a promise (refer to the example below) and use then (or await) to assign the resolved value to a variable. 

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

const result = await streamToString(stream)

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