gulpfile.js

'use strict';

const gulp       = require( 'gulp' );
const postcss    = require( 'gulp-postcss' );
// Use terser minifier with gulp-uglify for ES2015 support.
const composer   = require( 'gulp-uglify/composer' );
const terser     = require( 'terser' );
const minify     = composer( terser, console );
const sourcemaps = require( 'gulp-sourcemaps' );

const paths = {
	styles: {
		src: 'assets/styles/portfolio.css',
		dest: 'assets/styles/build/',
		watch: 'assets/styles/*.css'
	},
	scripts: {
		src: 'assets/scripts/*.js',
		dest: 'assets/scripts/build/'
	}
};

const processors = [
	require( 'postcss-import' ),
	require( 'postcss-nested' ),
	require( 'postcss-custom-properties' ),
	require( 'postcss-normalize' )( { forceImport: true } ),
	require( 'css-mqpacker' )( { sort: true } ),
	require( 'autoprefixer' ),
	require( 'cssnano' )( {
		preset: [ 'default', {
			calc: false,
			mergeLonghand: false // These conflict with processing nested calc() and env values().
		} ]
	} )
];

function styles() {
	return gulp.src( paths.styles.src )
		.pipe( sourcemaps.init() )
			.pipe( postcss( processors ) )
		.pipe( sourcemaps.write( './' ) )
		.pipe (gulp.dest( paths.styles.dest ) );
}

function scripts() {
	return gulp.src( paths.scripts.src )
		.pipe( sourcemaps.init() )
			.pipe( minify() )
		.pipe( sourcemaps.write( './' ) )
		.pipe( gulp.dest( paths.scripts.dest ) );
}

function watch() {
	gulp.watch( paths.styles.watch, styles );
	gulp.watch( paths.scripts.src, scripts );
}

// Workflows
// $ gulp: Builds, prefixes, and minifies CSS files; concencates and minifies JS files; watches for changes. The works.
const defaultTask = gulp.parallel( styles, scripts, watch );

// $ gulp build: Builds, prefixes, and minifies CSS files; concencates and minifies JS files. For const.
const buildTask = gulp.parallel( styles, scripts );

// Exports
// Externalise individual tasks.
exports.styles = styles;
exports.scripts = scripts;
exports.watch = watch;

// Externalise Workflows.
exports.build = buildTask;
exports.default = defaultTask;