http://www.100percentjs.com/just-like-grunt-gulp-browserify-now/ rewritten with best practices

gulpfile.js

var gulp = require('gulp');
var browserify = require('gulp-browserify');
var concat = require('gulp-concat');
var styl = require('gulp-styl');
var refresh = require('gulp-livereload');
var lr = require('tiny-lr');
var server = lr();

var paths = {
  js: 'src/**/*.js',
  styles: 'css/**/*.css'
};

gulp.task('scripts', function () {
  return gulp.src(paths.js)
    .pipe(browserify())
    .pipe(concat('dest.js'))
    .pipe(gulp.dest('build'))
    .pipe(refresh(server));
});

gulp.task('styles', function () {
  return gulp.src(paths.styles)
    .pipe(styl({
      compress: true
    }))
    .pipe(gulp.dest('build'))
    .pipe(refresh(server));
});

gulp.task('lr-server', function (cb) {
  server.listen(35729, cb);
});

gulp.task('watch', function () {
  gulp.watch(paths.js, ['scripts']);
  gulp.watch(paths.styles, ['styles']);
});

gulp.task('default', ['lr-server', 'scripts', 'styles', 'watch']);