Joins movies in a directory using ffmpeg.

join.js

const fs = require('fs')
const dir = process.argv[2]
const txtFilename = 'files.txt'
const outputFilename = 'output.mp4'
const { exec } = require('child_process')

let output = ''
const files = fs.readdirSync(dir).filter(f => (
  f !== '.DS_Store' &&
  f !== outputFilename &&
  ext(f) !== 'js' &&
  ext(f) !== 'txt')
).sort(naturalSort)

files.forEach(el => {
  output += `file '${el}'\n`
})
fs.writeFileSync(txtFilename, output, 'utf8')
exec(`ffmpeg -f concat -i ${txtFilename} -c copy ${outputFilename}`)
fs.unlinkSync(txtFilename)

function ext (p) {
  const e = p.split('.').pop().toLowerCase()
  return e
}

function naturalSort (a, b) {
  var re = /(^([+\-]?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?(?=\D|\s|$))|^0x[\da-fA-F]+$|\d+)/g,
    sre = /^\s+|\s+$/g,   // trim pre-post whitespace
    snre = /\s+/g,        // normalize all whitespace to single ' ' character
    dre = /(^([\w ]+,?[\w ]+)?[\w ]+,?[\w ]+\d+:\d+(:\d+)?[\w ]?|^\d{1,4}[\/\-]\d{1,4}[\/\-]\d{1,4}|^\w+, \w+ \d+, \d{4})/,
    hre = /^0x[0-9a-f]+$/i,
    ore = /^0/,
    i = function (s) {
      return (naturalSort.insensitive && ('' + s).toLowerCase() || '' + s).replace(sre, '')
    },
    // convert all to strings strip whitespace
    x = i(a),
    y = i(b),
        // chunk/tokenize
    xN = x.replace(re, '\0$1\0').replace(/\0$/, '').replace(/^\0/, '').split('\0'),
    yN = y.replace(re, '\0$1\0').replace(/\0$/, '').replace(/^\0/, '').split('\0'),
        // numeric, hex or date detection
    xD = parseInt(x.match(hre), 16) || (xN.length !== 1 && Date.parse(x)),
    yD = parseInt(y.match(hre), 16) || xD && y.match(dre) && Date.parse(y) || null,
    normChunk = function (s, l) {
            // normalize spaces; find floats not starting with '0', string or 0 if not defined (Clint Priest)
      return (!s.match(ore) || l == 1) && parseFloat(s) || s.replace(snre, ' ').replace(sre, '') || 0
    },
    oFxNcL, oFyNcL
    // first try and sort Hex codes or Dates
  if (yD) {
    if (xD < yD) { return -1 } else if (xD > yD) { return 1 }
  }
    // natural sorting through split numeric strings and default strings
  for (var cLoc = 0, xNl = xN.length, yNl = yN.length, numS = Math.max(xNl, yNl); cLoc < numS; cLoc++) {
    oFxNcL = normChunk(xN[cLoc] || '', xNl)
    oFyNcL = normChunk(yN[cLoc] || '', yNl)
        // handle numeric vs string comparison - number < string - (Kyle Adams)
    if (isNaN(oFxNcL) !== isNaN(oFyNcL)) {
      return isNaN(oFxNcL) ? 1 : -1
    }
        // if unicode use locale comparison
    if (/[^\x00-\x80]/.test(oFxNcL + oFyNcL) && oFxNcL.localeCompare) {
      var comp = oFxNcL.localeCompare(oFyNcL)
      return comp / Math.abs(comp)
    }
    if (oFxNcL < oFyNcL) { return -1 } else if (oFxNcL > oFyNcL) { return 1 }
  }
}