beforeunload 事件可以绑定到什么元素上面？

var attention = function (e) {
  var confirmationMessage = "修改尚未保存！";
  console.log(e.);
  (e || window.event).returnValue = confirmationMessage; // Gecko and Trident
  return confirmationMessage; // Gecko and WebKit
};

window.addEventListener('beforeunload', attention);

绑定到 window 上时起效，绑定到其他页面元素则不行，例如

var input = document.querySelector('table>input')
input.addEventListener('beforeunload', attention)