doublestream.js

var through2 = require('through2')
var fs = require('fs')
var byline = require('byline')

var combine = through2(function(chunk, enc, next){
  console.log(chunk.toString())
  console.log('--')
  next()
})

fs.readdir('./data', function(err, files){
  files.forEach(function(file){
    fs.createReadStream('./data/' + file)
      .pipe(byline.createStream())
      .pipe(combine)
  })
})