code: function on(dom, eventType, callback) {
    if (document.addEventListener) {
      dom.addEventListener(eventType, callback);
    } else {
      dom.attachEvent('on' + eventType, callback);
    }
  }
docs: 绑定事件
  
  @export
  @param {any} dom
  @param {any} eventType
  @param {any} callback