gulpfile.js

const gulp 		= require('gulp'),
	
	/** Plug-ins */
	// concat 		= require('gulp-concat'),
	htmlmin 	= require('gulp-htmlmin'),
	rename 		= require('gulp-rename'),
	sass 		= require('gulp-sass'),
	sourcemaps 	= require('gulp-sourcemaps'),
	terser 		= require('gulp-terser'),
	imagemin 	= require('gulp-imagemin'),
	
	/** Paths */
	in_root		= 'src',
	out_root	= 'dist',

	input = {
		'html': in_root + '/**/*.html',
		'styles': in_root + '/styles/**/*.scss',
		'js': in_root + '/js/**/*.js',
		'images': in_root + '/assets/**/*',
	},
	output = {
		'html': out_root,
		'styles': out_root + '/styles',
		// 'js': out_root + '/js',
		// 'images': out_root + '/assets',
		// 'styles': out_root,
		'js': out_root,
		'images': out_root,
	};

/** Process HTML files */
gulp.task('build-html', function () {
	return gulp.src(input.html)
		.pipe(htmlmin({
			collapseWhitespace: true,
			removeComments: true
		}))
		.pipe(gulp.dest(output.html));
});

/** Process Sass files */
gulp.task('build-styles', function () {
    return gulp.src(input.styles)
		.pipe(sourcemaps.init())
		.pipe(sass({
			errorLogToConsole: true,
			outputStyle: 'compressed'
        }))
        .on('error', console.error.bind(console))
        // OR
        // .pipe(sass().on('error', sass.logError))
		.pipe(rename({
            suffix: '.min'
        }))
        .pipe(sourcemaps.write())
        .pipe(gulp.dest(output.styles));
});

/** Process JS files */
gulp.task('build-js', function () {
	// return gulp.src(input.js)
	return gulp.src(input.js, { base: in_root })
		.pipe(sourcemaps.init())
        // .pipe(concat('site.js'))
        .pipe(terser({
			keep_fnames: false
		}))
        .pipe(rename({
            suffix: '.min'
        }))
		.pipe(sourcemaps.write())
        .pipe(gulp.dest(output.js));
});

/** Process image files */
gulp.task('imagemin', function () {
	return gulp.src(input.images)
		// .pipe(imagemin(
		// 	[
		// 		imagemin.jpegtran({
		// 			progressive: true
		// 		})
		// 	]
		// ))
		.pipe(gulp.dest(output.images));
});

/** Copy _redirect file */
gulp.task('copy_redir', function () {
	return gulp.src(in_root + '/_redirects')
		.pipe(gulp.dest(out_root));
});


/** Default task */
/** Image processing starts first, as it tends to require the longest execution */
gulp.task('default', 
	gulp.parallel(
		'imagemin', 
		'build-js', 
		'build-styles', 
		'build-html', 
		'copy_redir'
	)
);