gulpfile.js

let gulp        = require('gulp'),
    sass        = require('gulp-sass'),
    browserSync = require('browser-sync'),
    uglify      = require('gulp-uglify'),
    concat      = require('gulp-concat'),
    rename      = require('gulp-rename'),
    del         = require('del'),
    autoprefixer= require('gulp-autoprefixer'),
    csscomb     = require('gulp-csscomb');

gulp.task('clean',async function () {
    del.sync('dist')
});

gulp.task('scss',function () {
return gulp.src('app/scss/**/*.scss')
    .pipe(sass({outputStyle:'compressed'}))
    .pipe(autoprefixer({
        overrideBrowserslist:['last 8 versions']
    }))
    .pipe(rename({suffix:'.min'}))
    .pipe(gulp.dest('app/css'))
    .pipe(browserSync.reload({stream:true}))
});

gulp.task('stylus', function () {
return gulp.src('app/scss/**/*.scss')
    .pipe(csscomb())
    .pipe(gulp.dest('app/scss'))
    .pipe(browserSync.reload({stream:true}))
});

gulp.task('css',function () {
return gulp.src([
    'node_modules/normalize.css/normalize.css',
    'node_modules/slick-carousel/slick/slick.css',
])
    .pipe(concat('_libs.scss'))
    .pipe(gulp.dest('app/scss'))
    .pipe(browserSync.reload({stream:true}))

});

gulp.task('html',function () {
   return  gulp.src('app/*.html')
       .pipe(browserSync.reload({stream:true}))
});

gulp.task('script',function () {
    return  gulp.src('app/js/*.js')
        .pipe(browserSync.reload({stream:true}))
});

gulp.task('js',function () {
    return gulp.src([
        'node_modules/slick-carousel/slick/slick.js',
    ])
        .pipe(concat('libs.min.js'))
        .pipe(uglify())
        .pipe(gulp.dest('app/js'))
        .pipe(browserSync.reload({stream:true}))
});

gulp.task('browser-sync',function () {
    browserSync.init({
        server: {
            baseDir:'app/'
        }
    });
});

gulp.task('export', async function () {
   let buildHtml = gulp.src('app/**/*.html')
       .pipe(gulp.dest('dist'));

    let buildCss = gulp.src('app/css/**/*.css')
        .pipe(gulp.dest('dist/css'));

    let buildJs = gulp.src('app/js/**/*.js')
        .pipe(gulp.dest('dist/js'));

    let buildFonts = gulp.src('app/fonts/**/*.*')
        .pipe(gulp.dest('dist/fonts'));

    let buildImg = gulp.src('app/img/**/*.*')
        .pipe(gulp.dest('dist/img'));
});

gulp.task('watch', function () {
    gulp.watch('app/scss/**/*.scss', gulp.parallel('scss'));
    gulp.watch('app/*.html', gulp.parallel('html'));
    gulp.watch('app/js/*.js', gulp.parallel('script'));
});

gulp.task('build',gulp.series('clean','export'));

gulp.task('default',gulp.parallel('css','scss','js','browser-sync','watch'));