gulpfile.js

var gulp         = require('gulp'),
    jshint       = require('gulp-jshint'),
    rename       = require('gulp-rename'),
    uglify       = require('gulp-uglify'),
    babel        = require("gulp-babel"),
    postcss      = require('gulp-postcss'),
    cleanCSS     = require('gulp-clean-css'),
    cssbeautify  = require('gulp-cssbeautify'),
    autoprefixer = require('autoprefixer'),
    karma        = require('karma'),
    del          = require('del'),
    browserSync  = require('browser-sync').create(),
    path         = require('path');

// Source files
var SRC_JS = 'src/js/*.js';
var SRC_CSS = 'src/css/*.css';

// Destination folders
var DEST_JS = 'dist/js';
var DEST_CSS = 'dist/css';

// JS TASKS
// Lint JS
gulp.task('lint', function() {
    return gulp.src(SRC_JS)
        .pipe(jshint())
        .pipe(jshint.reporter('default'))
        .pipe(jshint.reporter('fail'));
});

// Build JS
gulp.task('build:js', ['clean:js', 'lint'], function() {
    return gulp.src(SRC_JS)
        .pipe(babel())
        .pipe(gulp.dest(DEST_JS))
        .pipe(uglify({ preserveComments: 'license' }))
        .pipe(rename({ suffix: '.min' }))
        .pipe(gulp.dest(DEST_JS))
});

// CSS TASKS
gulp.task('build:css', ['clean:css'], function() {
    return gulp.src(SRC_CSS)
        .pipe(postcss([autoprefixer({ browsers: ['last 10 versions'] })]))
        .pipe(cssbeautify({ autosemicolon: true }))
        .pipe(gulp.dest(DEST_CSS))
        .pipe(cleanCSS({ compatibility: 'ie8' }))
        .pipe(rename({ suffix: '.min' }))
        .pipe(gulp.dest(DEST_CSS));
});

// CLEAN files
gulp.task('clean', function() {
    gulp.start('clean:js', 'clean:css');
});

gulp.task('clean:js', function() {
    return del([DEST_JS]);
});

gulp.task('clean:css', function() {
    return del([DEST_CSS]);
});

// WATCH for file changes and rerun the task
gulp.task('watch', function() {
    gulp.watch('./src/js/*.js', ['build:js']);
    gulp.watch('./src/css/*.css', ['build:css']);
});

// TEST
gulp.task('test', function(done) {
    new karma.Server({
        configFile: __dirname + '/karma.conf.js',
        singleRun:  true
    }, function() {
        done();
    }).start();
});

gulp.task('browser-sync', ['watch'], function() {
    browserSync.init({
        startPath: "./examples",
        server: {
            baseDir: "./"
        }
    });

    gulp.watch("./examples/**/*").on("change", browserSync.reload);
    gulp.watch("./src/**/*").on("change", browserSync.reload);
    gulp.watch("./dist/**/*").on("change", browserSync.reload);
});

// DEFAULT task
gulp.task('default', function() {
    gulp.start('build:js', 'build:css');
});