gulpfile.js

var rename = require('gulp-rename');
var uglify = require('gulp-uglify');
var uglifycss = require('gulp-uglifycss');

var { src, dest, series, parallel, watch } = require('gulp');
var paths = {
	src: 'src/**/*',
	js: 'src/**/*.js',
	css: 'src/**/*.css',
	dist: './dist/',
};

function addMin(path) {
	path.basename += '.min';
}

function copy() {
	return src(paths.src).pipe(dest(paths.dist));
}

copy.description =
	'Copies src folder directly to the dist folder, no mutations';

function css() {
	var options = {
		maxLineLen: 80,
		uglyComments: true,
	};

	return src(paths.css)
		.pipe(uglifycss(options))
		.pipe(rename(addMin))
		.pipe(dest(paths.dist));
}

css.description =
	'Mutates the css files, including minifying, and adding ".min" to the basename';

function js() {
	var options = {
		compress: {
			hoist_funs: false,
		},
	};
	return src(paths.js)
		.pipe(uglify(options))
		.pipe(rename(addMin))
		.pipe(dest(paths.dist));
}

function source(done) {
	watch(paths.src, parallel(copy, css, js));
	done();
}

js.description =
	'Mutates the js files, including minifying, and adding ".min" to the basename';

exports.copy = copy;
exports.css = css;
exports.js = js;

exports.default = parallel(copy, css, js);
exports.dev = series(exports.default, source);