Gulp task system and Promises

Gulpfile.js

/**
 * Bluebird allows us to promisify existing Node.js
 * technologies. So fs.writeFile and fs.readFile
 * are usable with Promises.
 * 
 * `fetch` fetches Ressources. This code fetches
 * jQuery, and saves the responses body in a file
 **/

var gulp = require('gulp');
var Promise = require('bluebird');
var fs = Promise.promisifyAll(require('fs'));
var fetch = require('node-fetch');

gulp.task('fetch', function() {
  return fetch('http://code.jquery.com/jquery-2.1.4.min.js')
    .then(function(data) {
      return data.text();
    })
    .then(function(body) {
      return fs.writeFileAsync('jquery.js', body);
    });
});

When using Node.js 4, you can also use arrow functions:

  return fetch('http://code.jquery.com/jquery-2.1.4.min.js')
    .then(data => data.text())
    .then(body => fs.writeFileAsync('jquery.js', body));

Even better, use streams instead:

const fs = require('fs');
const http = require('http');

http.get('http://code.jquery.com/jquery-2.1.4.min.js', function (res) {
    res.pipe(fs.createWriteStream('jquery.js'));
});

Cool :-) I'm still new to all the Node 4 stuff ;-) With streams, I'd use the gulp API then.