gulpfile.js

const gulp = require('gulp');
const sass = require('gulp-sass');
const autoprefixer = require('gulp-autoprefixer');
const sourcemaps = require('gulp-sourcemaps');
const pug = require('gulp-pug');
const imagemin = require('gulp-imagemin');
const htmlValidator = require('gulp-w3c-html-validator');
const   through2 =      require('through2');
const htmlmin = require('gulp-htmlmin');
const browserSync = require('browser-sync').create();

//scss to css
function style() {
 return gulp.src('assets/scss/**/*.scss', { sourcemaps: true })
    .pipe(sass({
      // outputStyle: 'compressed'
    }).on('error', sass.logError))
    .pipe(autoprefixer('last 2 versions'))
         .pipe(gulp.dest('assets/css', { sourcemaps: '.' }));
}

// pug to html
function html() {
  return gulp.src('assets/pug/pages/theme/chart-widget.pug')
  .pipe(pug({ pretty: true }))
  .on('error', console.error.bind(console))
  .pipe(gulp.dest('theme'))
  .pipe(browserSync.reload({stream: true}));
}

//Html validator
function validateHtml() {
    function handleFile(file, encoding, callback) {
        callback(null, file);
        if (!file.w3cjs.success)
            throw new Error('HTML validation error(s) found');
    };
    return gulp.src('pages/*.html')
        .pipe(htmlValidator())
        .pipe(through2.obj(handleFile));
}

// minify images
function image() {
    return gulp.src('assets/virtual_images/*.*')
        .pipe(imagemin())
        .pipe(gulp.dest('assets/images'));
}

// minify html
function htmlminify() {
  return gulp.src('html/index.html')
    .pipe(htmlmin({ collapseWhitespace: true }))
    .pipe(gulp.dest('html/minify'));
}

// Watch function
function watch(){
  browserSync.init({
      proxy: 'home/savan/Desktop/finalxologit/theme/index.html'
  });
  gulp.watch('assets/scss/**/*.scss', style);
  gulp.watch('assets/pug/pages/theme/index.pug', html);
  gulp.watch('./*.html').on('change', browserSync.reload);
  gulp.watch('assets/css/*.css').on('change', browserSync.reload);
}

exports.style = style;
exports.html = html;
exports.watch = watch;
exports.image = image;
exports.validateHtml = validateHtml;
exports.htmlminify = htmlminify;

const build = gulp.series(watch);
gulp.task('default', build, 'browser-sync');