gulpfile.js

var gulp = require('gulp');

var del = require('del');
gulp.task('clean:min-css', function() {
	// Delete all *.min.css files in the css/ directory so we don't get duplicates
	return del([
		'css/*.min.css'
	]);
});
gulp.task('clean:min-js', function() {
	// Delete previously compiled global.min.js files in the js/ directory so we don't get duplicates
	return del([
		'js/global.min.js'
	]);
});

var concat = require('gulp-concat');
var uglify = require('gulp-uglify');
var wpIncludesDir = '../../../wp-includes/js';
gulp.task('js', ['clean:min-js'], function() {
	return gulp.src([
		// wpIncludesDir + '/jquery/jquery.js',
		wpIncludesDir + '/jquery/jquery-migrate.js',
		wpIncludesDir + '/wp-embed.js',
		wpIncludesDir + '/wp-emoji-release.min.js',
		wpIncludesDir + '/mediaelement/mediaelement-and-player.min.js',
		wpIncludesDir + '/mediaelement/wp-mediaelement.js',
		'js/menu.js',
		'js/analytics.js'
	])
		.pipe( concat('global.min.js') )
		.pipe( uglify() )
		.pipe( gulp.dest('js/') );
});

var foreach = require('gulp-foreach');
var path = require('path');
var concatCSS = require('gulp-concat-css');
var autoprefixer = require('gulp-autoprefixer');
var cssnano = require('gulp-cssnano');
gulp.task('css', ['clean:min-css'], function() {
	gulp.src('css/*.css')
		.pipe(
			// Loop over each stream, figure out the filename, and run the stream through concatCSS() passing along the dynamic filename
			foreach(function(stream, file) {
				// Get the filename without the extension...
				var filename = path.basename(file.path, '.css');

				return stream.pipe( concatCSS(filename + '.min.css') )
			})
		)

		// Autoprefix
		.pipe( autoprefixer() )

		// minify CSS
		.pipe( cssnano() )

		// Save out the new file
		.pipe( gulp.dest('css/') );
});

gulp.task('default', ['css', 'js'] );