gulpfile.js

var gulp = require('gulp')
var concat = require('gulp-concat')
var uglify = require('gulp-uglify')
var rename = require('gulp-rename')
var minifyCSS = require('gulp-minify-css')
var postcss = require('gulp-postcss')
var sourcemaps = require('gulp-sourcemaps')
var autoprefixer = require('autoprefixer')
var browserify = require('browserify')
var source = require('vinyl-source-stream')
var buffer = require('vinyl-buffer')

var paths = {
  root: './',
  index: './index.html',

  src: {
    css: './src/css/*css',
    js: './src/js/*.js',
    jsIndex: './src/js/index.js',
    jsMain: './src/js/material-photo-gallery.js'
  },

  dist: {
    css: './dist/css',
    js: './dist/js',
    bundle: './dist/js/bundle.js'
  }
}

gulp.task('watch', ['css', 'browserify'], function() {
  gulp.watch(paths.src.css, ['css'])
  gulp.watch(paths.src.js, ['browserify'])
})

gulp.task('css', function() {
  return gulp
    .src(paths.src.css)
    .on('error', handleError)
    .pipe(postcss([autoprefixer()]))
    .pipe(minifyCSS())
    .pipe(gulp.dest(paths.dist.css))
})

gulp.task('browserify', function() {
  return browserify(paths.src.jsIndex)
    .bundle()
    .on('error', handleError)
    .pipe(source('material-photo-gallery.js'))
    .pipe(buffer())
    .pipe(gulp.dest(paths.dist.js))
    .pipe(uglify())
    .pipe(rename('material-photo-gallery.min.js'))
    .pipe(gulp.dest(paths.dist.js))
})

// Handle errors and continue watching files
function handleError(err) {
  console.log(err.toString())
  this.emit('end')
}

gulp.task('default', ['css', 'browserify'])