code: function off(dom, eventType, callback) {
    if (document.addEventListener) {
      dom.removeEventListener(eventType, callback);
    } else {
      dom.detachEvent('on' + eventType, callback);
    }
  }
docs: 解绑事件
  
  @export
  @param {any} dom
  @param {any} eventType
  @param {any} callback