Gulp: Grabbing JavaScript assets from a CDN to add to your build pipeline

Gulpfile.js

var gulp = require('gulp');
var source = require('vinyl-source-stream');
var request = require('request');
var merge = require('merge2');
var concat = require('gulp-concat');
var buffer = require('gulp-buffer');

/** 
 * 1. We request the latest jQuery version from the jQuery CDN. The
 *    request package allows for streaming. What we get in return
 *    is a readable stream.
 * 2. We create a valid vinyl file object with vinyl source stream
 *    This makes it compatible with Gulp
 * 3. Our main file is selected from the file system as usual
 * 4. The merge2 package allows us to combine both streams
 * 5. The contents of both streams are converted to text buffers
 *    so gulp-concat can handle them.
 */

gulp.task('js', function() {
  
  var jquery = request('http://code.jquery.com/jquery-latest.js') /* 1 */
    .pipe(source('jquery.js'));                                   /* 2 */
  var main = gulp.src('main.js');                                 /* 3 */

  return merge(jquery, main)                                      /* 4 */
    .pipe(buffer())                                               /* 5 */
    .pipe(concat('main.min.js'))
    .pipe(gulp.dest('dist'));
})