gulpfile.js

var gulp = require('gulp'),
    sass = require('gulp-ruby-sass'),
    autoprefixer = require('gulp-autoprefixer'),
    minifycss = require('gulp-minify-css'),
    jshint = require('gulp-jshint'),
    uglify = require('gulp-uglify'),
    imagemin = require('gulp-imagemin'),
    rename = require('gulp-rename'),
    concat = require('gulp-concat'),
    notify = require('gulp-notify'),
    cache = require('gulp-cache'),
    del = require('del'),
    browserSync = require('browser-sync').create();

gulp.task('default', ['clean', 'styles', 'scripts', 'images', 'watch'], function() {
  browserSync.init({
    proxy: "localhost:8000"
  });
  gulp.watch('**/*.html').on('change', browserSync.reload);
  gulp.watch(['static/**']).on('change', browserSync.reload);
});

gulp.task('styles', function() {
  return sass('assets/sass/main.scss', { style: 'expanded' })
    .pipe(autoprefixer('last 2 version'))
    .pipe(gulp.dest('static/css'))
    .pipe(rename({suffix: '.min'}))
    .pipe(minifycss())
    .pipe(gulp.dest('static/css'))
});

gulp.task('scripts', function() {
  return gulp.src('assets/js/**/*.js')
    .pipe(jshint.reporter('default'))
    .pipe(concat('main.js'))
    .pipe(gulp.dest('static/js'))
    .pipe(rename({suffix: '.min'}))
    .pipe(uglify())
    .pipe(gulp.dest('static/js'))
    .pipe(notify({ message: 'Scripts task complete' }));
});

gulp.task('images', function() {
  return gulp.src('assets/img/*')
    .pipe(cache(imagemin({ optimizationLevel: 3, progressive: true, interlaced: true })))
    .pipe(gulp.dest('static/img'))
});

gulp.task('clean', function() {
    return del(['static/css', 'static/js', 'static/img']);
});

gulp.task('watch', function() {
  gulp.watch('assets/sass/**/*.scss', ['styles']);
  gulp.watch('assets/js/**/*.js', ['scripts']);
  gulp.watch('assets/img/**/*', ['images']);
});