http://zccst.iteye.com/blog/2194229

 

获取用户的联网状态

if (navigator && navigator.onLine === false) {  alert("无法连接网络")}else{ alert("正常上网")}

 

监听事件

var el = document.body;  if (el.addEventListener) {     window.addEventListener("online", function () {       alert("online");}, true);     window.addEventListener("offline", function () {       alert("offline");}, true);  }  else if (el.attachEvent) {     window.attachEvent("ononline", function () {       alert("online");});     window.attachEvent("onoffline", function () {       alert("offline");});  }  else {     window.ononline = function () {       alert("online");};     window.onoffline = function () {       alert("offline");};  }