dw/gulpfile.js

const gulp = require('gulp'),
      useref = require('gulp-useref'),
      gulpif = require('gulp-if'),
      uglify = require('gulp-uglify'),
      cleanCSS = require('gulp-clean-css'),
      rename = require("gulp-rename"),
      concat = require("gulp-concat"),
      browserSync = require('browser-sync').create();

gulp.task('copy', async function() {
  gulp.src('./node_modules/bootstrap/dist/css/bootstrap.css')
    .pipe(gulp.dest('./css/'));
  gulp.src('./node_modules/bootstrap/dist/js/bootstrap.js')
    .pipe(gulp.dest('./js/'));
  gulp.src('./node_modules/jquery/dist/jquery.min.js')
    .pipe(gulp.dest('./js/'));
  console.log("Files copied from npm packages");
});

gulp.task('build', async function() {
  gulp.src('./css/bootstrap.css','./css/style.css')
    .pipe(concat('style.min.css'))
    .pipe(gulp.dest('./app/css/'));
  gulp.src('index.html')
    .pipe(useref())
    .pipe(gulpif('*.js', uglify()))
    .pipe(gulpif('*.css', cleanCSS({level: {1: {specialComments: 0}}})))
    .pipe(gulp.dest('./app/'));
  console.log("Assets packaged for app/");
});

function run() {
  browserSync.init({
    server: {
      baseDir: "./",
      index: "/index.html"
    }
  });
  gulp.watch('./css/**/*.css').on('change', browserSync.reload);;
  gulp.watch('./*.html').on('change',browserSync.reload);
  gulp.watch('./js/**/*.js').on('change', browserSync.reload);
}

exports.run = run;