gulpfile.js

var gulp = require('gulp');
var gulpif = require('gulp-if');
var sass = require('gulp-sass');
var autoprefixer = require('gulp-autoprefixer');
var minify = require('gulp-clean-css');
var babel = require('gulp-babel');
var uglify = require('gulp-uglify');
var rename = require('gulp-rename');
var del = require('del');
var runSequence = require('run-sequence');
var browserSync = require('browser-sync');
var plumber = require('gulp-plumber');

var BUILD = false;

const path = {
  HTML: 'src/index.html',
  CSS: 'src/css/*',
  CSS_ENTRY: 'src/css/style.scss',
  JS: 'src/js/*',
  JS_ENTRY: 'src/js/Component.jsx',

  DEST: 'dev',
  DEST_CSS: 'dev/css',
  DEST_JS: 'dev/js',
};

const onError = function(err) {
  console.log(err);
};

gulp.task('production', () => {
  BUILD = true;

  path.DEST = 'public';
  path.DEST_CSS = 'public/css';
  path.DEST_JS = 'public/js';
  return;
});

gulp.task('clean', () => {
  return del.sync(path.DEST);
});

gulp.task('copy-html', () => {
  return gulp.src(path.HTML)
    .pipe(gulp.dest(path.DEST));
});

gulp.task('css', () => {
  return gulp.src(path.CSS_ENTRY)
    .pipe(sass().on('error', sass.logError))
    .pipe(autoprefixer())
    .pipe(gulpif(BUILD, minify()))
    .pipe(gulp.dest(path.DEST_CSS));
});

gulp.task('js', () => {
  return gulp.src(path.JS_ENTRY)
    .pipe(plumber({
      errorHandler: onError
    }))
    .pipe(babel({
      presets: ['es2015', 'stage-0', 'react']
    }))
    .pipe(gulpif(BUILD, uglify()))
    .pipe(rename('script.js'))
    .pipe(gulp.dest(path.DEST_JS));
});

gulp.task('browser-sync', () => {
  browserSync.init(path.DEST, {
    server: {
      baseDir: "./dev"
    }
  });
});

gulp.task('watch', ['browser-sync'], () => {
  gulp.watch(path.CSS, ['css']);
  gulp.watch(path.HTML, ['copy-html']);
  gulp.watch(path.JS, ['js']);
});

gulp.task('dev', function() {
  runSequence('clean', ['watch', 'copy-html', 'css', 'js']);
});

gulp.task('default', ['dev']);

gulp.task('build', function() {
  runSequence('production', 'clean', ['copy-html', 'css', 'js']);
});