gulpfile.js

var gulp = require('gulp'),
    concat = require('gulp-concat'),
    uglify = require('gulp-uglify'),
    rename = require('gulp-rename'),
    sass = require('gulp-ruby-sass'),
    autoprefixer = require('gulp-autoprefixer');

var DEST = 'static/';

gulp.task('images', function() {
    return gulp.src('ui/images/*')
        .pipe(gulp.dest(DEST + '/images'));
});

gulp.task('scripts', function () {
    return gulp.src([
        'ui/js/helpers/*.js',
        'ui/js/*.js',
    ])
        .pipe(concat('custom.js'))
        .pipe(gulp.dest(DEST + '/js'))
        .pipe(rename({ suffix: '.min' }))
        .pipe(uglify())
        .pipe(gulp.dest(DEST + '/js'));
});

var compileSASS = function (filename, options) {
    return sass('ui/scss/*.scss', options)
        .pipe(autoprefixer('last 2 versions', '> 5%'))
        .pipe(concat(filename))
        .pipe(gulp.dest(DEST + '/css'));
};

gulp.task('sass', function () {
    return compileSASS('custom.css', {});
});

gulp.task('sass-minify', function () {
    return compileSASS('custom.min.css', { style: 'compressed' });
});

// Default Task
gulp.task('default', ['images', 'scripts', 'sass', 'sass-minify']);