js访问公网服务器实例

checkNet().then(function(res) {
 if(res) {
 //连网成功 
 }
 } else {
 //连网失败 
 }
})

(function() {
 //检测入口
 checkNet = function() {
 var def = $.Deferred();
 xiuNet(null).then(function(res) {
 netWork(null).then(function(res) {
 if(res) {
 def.resolve(true);
 } else {
 def.resolve(false);
 }
 })
 })
 return def.promise();
 }
 
 //嗅探网络，解决ios弹框接入网络问题
 var checkTime = 2; //嗅探次数
 xiuNet = function(def) {
 if(def == null) {def = $.Deferred();}
 var iframe = document.createElement("iframe");
 iframe.style.cssText = "display:none;width:0px;height:0px;";
 document.body.appendChild(iframe);
 var ua = navigator.userAgent;
 if(ua.indexOf("iPhone") != -1 || ua.indexOf("iPod") != -1 ||ua.indexOf("iPad") != -1) {
 iframe.src = "http://www.baidu.com" + "?timestap=" + new Date().getTime();
 console.info("嗅探网络----");
 if(checkTime > 1) {
 checkTime--;
 setTimeout(function() {
 xiuNet(def)
 }, 1000);
 } else {
 def.resolve(true);
 }
 } else {
 def.resolve(false);
 }
 return def.promise();
 }

 //检测网络，是否可以连接公网
 var cnetTime = 3; //检测网络次数
 netWork = function(def) {
 if(def == null) {def = $.Deferred();}
 $.ajax({
 type: "get",
 timeout: 2000,
 dataType: "jsonp",
 jsonp: "callback",
 url: 'https://jktv.tv/shphone/ver.txt',
 success: function(data) {},
 error: function(xhr) {
 $("#ddd").html("status:"+xhr.status)
 if(xhr.readyState == 4 && xhr.status == 200) {
 def.resolve(true);
 } else {
 if(cnetTime > 1) {
 cnetTime--;
 setTimeout(function() {
 netWork(def)
 }, 200);
 } else {
 def.resolve(false);
 }
 }
 }
 });
 return def.promise();
 }
})();