A simple javascript (node) script used to download items of a youtube playlist as audio files

yt.js

//
// Dependency : [youtube-dl](https://github.com/ytdl-org/youtube-dl)
//
// How to use :
// 
//  - install targetFolder : `pip install --upgrade youtube-dl`
//  - Go to a YouTube playlist (eg: https://www.youtube.com/playlist?list=PLzCxunOM5WFLNCSF0UEHZqFJJlmdeL71S)
//  - The ID is `PLzCxunOM5WFLNCSF0UEHZqFJJlmdeL71S`
//  - Update the const `playlistId`.
//  - Grab a YouTube Data API token in https://console.developers.google.com
//  - Update the const `key`
//  - [Optional]: change the const `targetFolder` to put audio files in another folder than the default one (current script path).
//  - Execute the script : `node ./yt.js`
//  - Be patient, it will take a long time to download, especially if the playlist has much items..
//

// Config
const host         = 'https://www.googleapis.com/youtube/v3'
const watchUrl     = 'https://www.youtube.com/watch?v='
const key          = '<YOUR_YOUTUBE_API_KEY>'
const playlistId   = '<TARGET_PLAYLIST_ID>'
const targetFolder = 'mp3'

// Libs
const https         = require('https');
const { spawnSync } = require( 'child_process' );

// Data
var commands = []

// Base functions

function GET(path, params, callback) {
  let urlParams = ''

  for (let key in params) {
    urlParams = urlParams
      .concat('&')
      .concat(key)
      .concat('=')
      .concat(params[key])
  }

  console.log(host + path + '?key=' + key + urlParams)

  https.get(host + path + '?key=' + key + urlParams, (response) => {
    let data = '';

    response.on('data', (chunk) => {
      data += chunk;
    });

    response.on('end', () => {
      callback(JSON.parse(data))
    })
  })
}

function fetchPage(pageToken, callback) {
  let params = {
    playlistId: playlistId,
    part: 'contentDetails',
    maxResults: 50
  }

  if (pageToken !== undefined) {
    params.pageToken = pageToken
  }

  GET('/playlistItems', params, (data) => {
    for (let item of data.items) {
      let command = [
        'youtube-dl',
        '-x',
        '--audio-quality', '0',
        '--audio-format', 'mp3',
        '-o', targetFolder + '/%(title)s-%(id)s.%(ext)s',
        watchUrl + item.contentDetails.videoId
      ]

      commands.push(command)
    }

    if (data.nextPageToken !== undefined) {
      fetchPage(data.nextPageToken, callback)
    } else {
      callback()
    }
  })
}

// Main

fetchPage(undefined, function() {
  for (let cmd of commands) {
    console.log('spawning ' + cmd.join(' '))
    const extracting = spawnSync(cmd.shift(), cmd)
    console.log(extracting.stderr.toString())
    console.log(extracting.stdout.toString())
  }
})