Spotify-dl: A NodeJS script to download spotify tracks from youtube. Depends on node-fetch and youtube-dl.

spotify-dl.bat

@echo off

SET CLIENT_ID=
SET CLIENT_SECRET=
SET YOUTUBE_KEY=

node PATH\TO\SCRIPT\spotify-dl.js %1

rem %1 track link
rem this file may be added to your env to quickly execute the script anywhere on your pc.

spotify-dl.js

// # About
// This script downloads spotify tracks as mp3 files.
// Please state the source if your share this.
//
// MAKE SURE TO ADD CLIENT_ID, CLIENT_SECRET, AND YOUTUBE_KEY TO YOUR ENV. MORE
// INFO BELOW!
//
// # Getting Started
// This script depends on youtube-dl and node-fetch.
// > npm i -g node-fetch
// > http://ytdl-org.github.io/youtube-dl/download.html
//
// The script first authorises with Spotify then tries to fetch the track you
// passed based on the parsed track id. If it's successful it'll authenticate
// with YouTube to search youtube for the title of the track, and using the
// first result passed the found video URL to youtube-dl. Youtube-dl downloads
// and transforms the audio to the popular mp3.
// https://github.com/kl13nt

/**
 * @param {string} CLIENT_ID Your spotify app client id
 * @param {string} CLIENT_SECRET Your spotify app client secret
 * @link https://developer.spotify.com/documentation/general/guides/authorization-guide/#client-credentials-flow
 *
 * @param {string} YOUTUBE_KEY Your youtube api key
 * @link https://developers.google.com/youtube/v3/guides/auth/server-side-web-apps#prerequisites
 */
const { CLIENT_ID, CLIENT_SECRET, YOUTUBE_KEY } = process.env

const child = require('child_process')
const path = require('path')
const fetch = require('node-fetch')

const terminateWithError = (error = '[fatal] error') => {
	console.log(error)
	process.exit(1)
}

const params = process.argv.slice(2)
if (params.length < 1) terminateWithError('[fatal] need spotify track url')

const id = params[0].match(
	/https:\/\/open?\.?spotify\.com\/track\/(\S+)\?\S+/i
)[1]

const DOWNLOADS = 'C:\\Users\\<USER_NAME>\\Downloads'
const SPOTIFY_AUTH = 'https://accounts.spotify.com/api/token'
const SPOTIFY_API = 'https://api.spotify.com'
const WATCH = 'https://www.youtube.com/watch?v='

let name = ''
let output = ''

fetch(`${SPOTIFY_AUTH}?grant_type=client_credentials`, {
	method: 'POST',
	headers: {
		'Content-Type': 'application/x-www-form-urlencoded',
		Authorization:
			'Basic ' + Buffer.from(CLIENT_ID + ':' + CLIENT_SECRET).toString('base64')
	}
})
	.then(async res => {
		if (!res.ok) {
			terminateWithError(`[fatal] spotify auth status ${res.status}`)
		}
		console.log('[info] spotify auth successful')

		return res.json()
	})
	.then(auth => {
		// https://github.com/spotify/web-api-auth-examples/blob/master/client_credentials/app.js#L31
		const token = auth.access_token

		const options = {
			headers: {
				Authorization: 'Bearer ' + token
			}
		}

		return fetch(`${SPOTIFY_API}/v1/tracks/${id}`, options)
	})
	.then(res => {
		if (!res.ok) terminateWithError(`[fatal] spotify status ${res.status}`)

		return res.json()
	})
	.then(track => {
		if (!track) terminateWithError('[fatal] track not found')

		name = encodeURIComponent(track.name)
		const YOUTUBE_API = `https://www.googleapis.com/youtube/v3/search?part=snippet&maxResults=1&q=${name}&key=${YOUTUBE_KEY}`

		return fetch(YOUTUBE_API)
	})
	.then(res => {
		if (!res.ok) terminateWithError(`[fatal] youtube status ${res.status}`)

		return res.json()
	})
	.then(json => {
		const { videoId } = json.items[0].id

		console.log(`[info] Fetching track ${WATCH}${videoId}`)

		output = path.resolve(DOWNLOADS, name).replace(/%20/gi, '_')
		const cmd = `youtube-dl`
		const args = [
			'-f',
			'bestaudio',
			'--extract-audio',
			'--audio-format',
			'mp3',
			'--audio-quality',
			'0',
			'-o',
			`"${output}.%(ext)s"`,
			`${WATCH}${videoId}`
		]

		console.log(`[info] ${cmd} ${args.join(' ')}`)
		const ydl = child.spawn(cmd, args)

		ydl.stdout.on('data', data => {
			console.log(`[info] ${data}`)
		})

		ydl.stderr.on('data', data => {
			console.log(`[fatal] ${data}`)
		})

		ydl.on('close', code => {
			console.log(`[info] youtube_dl exited with code ${code}`)
		})
	})
	.catch(error => terminateWithError(`[fatal] ${error} ${error.stack}`))