gulpfile.js

const gulp = require("gulp"),
	browserify = require("browserify"),
	babelify = require("babelify"),
	buffer = require("vinyl-buffer"),
	source = require("vinyl-source-stream"),
	cssnano = require("cssnano"),
	postcss = require("gulp-postcss"),
	uglify = require("gulp-uglify"),
	htmlmin = require("gulp-htmlmin"),
	del = require("del");

const paths = {
	source: "./src",
	build: "./build"
};

function cleanup() {
	return del([paths.build]);
}

function javascriptBuild() {
	return browserify({
		entries: [`${paths.source}/scripts/main.js`],
		debug: true,
		transform: [
			babelify.configure({
				presets: ["@babel/preset-env"]
			})
		]
	})
		.bundle()
		.pipe(source("bundle.js"))
		.pipe(buffer())
		.pipe(uglify())
		.pipe(gulp.dest(`${paths.build}/scripts/`));
}

function htmlBuild() {
	return gulp
		.src(`${paths.source}/*.html`)
		.pipe(htmlmin({ collapseWhitespace: true }))
		.pipe(gulp.dest(paths.build));
}

function cssBuild() {
	return gulp
		.src(`${paths.source}/styles/**/*.css`)
		.pipe(postcss([cssnano()]))
		.pipe(gulp.dest(`${paths.build}/styles`));
}

exports.default = exports.build = gulp.series(cleanup, gulp.parallel(javascriptBuild, htmlBuild, cssBuild));