require.css

// init, append require.css method
(function() {
  var list = {};
  // 移除css
  var remove = function remove() {
    this.count --;
    if (this.count <= 0) {
      this.$style.remove();
    }
  }
  require.css = function(src) {
    if (list[src]) {
      list[src].count ++;
    } else {
      list[src] = {
        count: 0, 
        remove: remove
      };
      var $style = document.createElement('style');
      $style.textContent = require(src, 'css');
      var $head = document.getElementByTag('head')[0];
      $head.appendChild($style);
      list[src].$style = $head;
    }
    return list[src];
  }
})(require);

// in vue demo
var $css = require.css('./style.css');
new Vue({
  template: require('./index.html', 'html'),
  destroyed: function() {
    $css.remove();
  }
});