gulpfile.js

const gulp = require('gulp');
const sass = require('gulp-sass');
const sourcemaps = require('gulp-sourcemaps');
const browserify = require('gulp-browserify');
const autoprefixer = require('gulp-autoprefixer');
const uglify = require('gulp-uglify');
const babel = require('gulp-babel');
const fileinclude = require('gulp-file-include');

gulp.task('default', () => {
	gulp.watch('./assets/stylesheets/src/**/*.scss', ['sass']);
	gulp.watch('./assets/js/src/**/*.js', ['js']);
	gulp.watch('./src/**/*.html', ['fileinclude']);
	gulp.watch('./src/*.html', ['fileinclude']);
});

gulp.task('sass', () => {
	return gulp.src('./assets/stylesheets/src/**/*.scss')
		.pipe(sourcemaps.init())
		.pipe(sass({outputStyle: 'compressed'}).on('error', sass.logError))
		.pipe(autoprefixer({
			browsers: ['last 50 versions'],
			cascade: false
		}))
		.pipe(sourcemaps.write('./sourcemaps'))
		.pipe(gulp.dest('./assets/stylesheets/build'));
});

gulp.task('js', () => {
	return gulp.src('./assets/js/src/*.js')
		.pipe(sourcemaps.init())
		.pipe(
			browserify({
				insertGlobals : true,
				debug : !gulp.env.production
			})
		)
		.pipe(babel({
			presets: ["es2015"]
		}))
		.pipe(uglify())
		.pipe(sourcemaps.write('./sourcemaps'))
		.pipe(gulp.dest('./assets/js/dist'));
});

gulp.task('fileinclude', function() {
  gulp.src(['src/*.html'])
    .pipe(fileinclude({
      prefix: '@@',
      basepath: '@file'
    }))
    .pipe(gulp.dest('./'));
});