NodeJS: Read csv file from sftp server and convert it to JSON

I am using ssh2-sftp-client to read a CSV file and create a ReadableStream. Then I am trying to convert this readableStream to Json with the help of the library csvtojson. However, I always get the following error:

TypeError: readStream.pipe is not a function

Here is my code so far:

let Client = require('ssh2-sftp-client');
let sftp = new Client();
var csv = require("csvtojson");

sftp.connect({
    host: 'HOST',
    port: 'PORT',
    username: 'USERNAME',
    password: 'PASSWORD'
}).then(() => {
    return sftp.get('/home/user/etc/testfile.csv');
}).then((data) => {
    csv()
        .fromStream(data)
        .subscribe(function (jsonObj) { //single json object will be emitted for each csv line
            // parse each json asynchronousely
            return new Promise(function (resolve, reject) {
                resolve()
                console.log(jsonObj);
            })
        })

}).catch((err) => {
    console.log(err, 'catch error');
});

Does anyone know if I am using both libraries correctly or whether it is not possible what I try to achieve?

You are getting an error because sftp.get returns a Buffer and you're trying to pass it to a function that expects a Stream.

Change your code to this

let Client = require('ssh2-sftp-client');
let sftp = new Client();
var csv = require("csvtojson");

sftp.connect({
  host: 'HOST',
  port: 'PORT',
  username: 'USERNAME',
  password: 'PASSWORD'
}).then(() => {
  return sftp.get('/home/user/etc/testfile.csv');
}).then((data) => {
  csv()
    .fromString(data.toString()) // changed this from  .fromStream(data)
    .subscribe(function(jsonObj) { //single json object will be emitted for each csv line
      // parse each json asynchronously
      return new Promise(function(resolve, reject) {
        resolve()
        console.log(jsonObj);
      })
    })
}).catch((err) => {
  console.log(err, 'catch error');
});