code: function(target, eventType, callback) {
      if (target.addEventListener) {
        target.addEventListener(eventType, callback, false);
        return {
          remove: function() {
            target.removeEventListener(eventType, callback, false);
          }
        };
      } else if (target.attachEvent) {
        target.attachEvent('on' + eventType, callback);
        return {
          remove: function() {
            target.detachEvent('on' + eventType, callback);
          }
        };
      }
    }
docs: Listen to DOM events during the bubble phase.
  
  @param {DOMEventTarget} target DOM element to register listener on.
  @param {string} eventType Event type, e.g. 'click' or 'mouseover'.
  @param {function} callback Callback function.
  @return {object} Object with a `remove` method.