Роман Огарков

function checkLength(arr) {
  if (arr.length && arr.isArray()) {

  }
}

'use strict';
const gulp        = require('gulp');
const browserSync = require('browser-sync').create();
const uglify      = require('gulp-uglify');
const useref      = require('gulp-useref');
const rename      = require('gulp-rename');
const browserify  = require('browserify');
const babelify    = require('babelify');
const buffer      = require('vinyl-buffer');
const source      = require('vinyl-source-stream');
const sourcemaps  = require('gulp-sourcemaps');

// use default task to launch Browsersync and watch JS files
gulp.task('serve', ['js'], () => {

	// Serve files from the root of this project
	browserSync.init({
		proxy: "localhost"
	});

	// add browserSync.reload to the tasks array to make
	// all browsers reload after tasks are complete.
	gulp.watch("src/*.js", ['js']);
	gulp.watch("*.html").on("change", browserSync.reload);
	gulp.watch("dist/*.js").on("change", browserSync.reload);
	gulp.watch("ssi/*.shtml").on("change", browserSync.reload);
	gulp.watch("css/*.css").on("change", browserSync.reload);
});

// process JS files and return the stream.
gulp.task('js', () => {
	let bundler = browserify({
		entries: 'src/main.js',
		debug: true
	});

	bundler
	.transform(babelify, {
			presets: ['es2015'],
			compact: false,
			ignore: /libs/
	})
	.transform('browserify-shim');
	bundler.bundle()
		.on('error', err => console.error(err))
		.pipe(source('main.js'))
		.pipe(buffer())
		.pipe(sourcemaps.init({ loadMaps: true }))
		.pipe(uglify())
		.pipe(sourcemaps.write('./'))
		.pipe(rename({suffix: '.min'}))
		.pipe(gulp.dest('dist'))
		.pipe(browserSync.stream());
});
// create a task that ensures the `js` task is complete before
// reloading browsers
gulp.task('default', ['serve']);

$('.js-func').on('click', function(event) {
		event.preventDefault();
		my_func();
	});

Чтобы написать чистый код, мы сначала пишем грязный код, а затем рефакторим его.
Robert Martin