Updated gulpfile to use modern syntax

gulpfile.js

@@ -2,16 +2,18 @@
 
 // Import required modules
 const del = require('del');
-const gulp = require('gulp');
+const { dest, series, src, watch }  = require('gulp');
 const postcss = require('gulp-postcss');
 const sass = require('gulp-sass')(require('sass'));
 
 // Set src and destination paths for css compilation
-const src = 'src/stylesheets/main.scss';
-const dest = 'public/css';
+const cssPaths = {
+	src: 'src/stylesheets/main.scss',
+	dest: 'public/css'
+};
 
-// Task to compile and optimise css from sass file
-gulp.task('styles', () => {
+// Compile and optimise css from sass file
+function compileStyles() {
 	let cssnanoOptions = {
 		normalizeWhitespace: false
 	};
@@ -27,25 +29,21 @@ gulp.task('styles', () => {
 		require('postcss-sort-media-queries')
 	];
 
-	return gulp.src(src)
+	return src(cssPaths.src)
 		.pipe(sass().on('error', sass.logError))
 		.pipe(postcss(plugins))
-		.pipe(gulp.dest(dest));
-});
+		.pipe(dest(cssPaths.dest));
+}
 
-// Task to clean up the destination directory
-gulp.task('clean', () => {
-	return del([
-		dest
-	]);
-});
+// Clean css destination directory
+function cleanStyles() {
+	return del([ cssPaths.dest ]);
+}
 
-// When called with no task, clean the destination, and then compile styles
-gulp.task('default', gulp.series([ 'clean', 'styles' ]));
+// Task to build stylesheet from start to finish
+exports.styles = series(cleanStyles, compileStyles);
 
 // Task to watch for changes in sass files, then compile on changes
-gulp.task('watch', () => {
-	gulp.watch('src/stylesheets/**/*.scss', (done) => {
-		gulp.series([ 'clean', 'styles' ])(done);
-	});
-});
+exports.watchStyles = () => {
+	watch('src/stylesheets/**/*.scss', exports.styles);
+};