promise when there's no argument

README.md

@@ -354,10 +354,10 @@ This script parses a couple of flags from `argv`:
 
 ### Update (promise version)
 
-If you are using promises there's now a promise version.
+If you are using promises there's now a promise version, if you don't pass a function as second argument:
 
 ``` js
-const downloader = require('youtube-dl/lib/downloaderPromise')
+const downloader = require('youtube-dl/lib/downloader')
 
 downloader('path/to-binary')
 .then((message) => {

lib/downloader.js

@@ -4,6 +4,7 @@ const request = require('request')
 const mkdirp = require('mkdirp')
 const path = require('path')
 const fs = require('fs')
+const util = require('util')
 
 const [, , ...flags] = process.argv
 
@@ -77,6 +78,9 @@ function downloader (binDir, callback) {
     callback = binDir
     binDir = null
   }
+  else if (!callback) {
+    return util.promisify(downloader)(binDir)
+  }
 
   createBase(binDir)
 

scripts/download.js

@@ -1,6 +1,7 @@
 var downloader = require('../lib/downloader')
 
-downloader(function error (err, done) {
-  if (err) return console.log(err.stack)
-  console.log(done)
-})
+downloader().then((message) => {
+  console.log(message);
+}).catch((err) => {
+  console.error(err)
+});