ajax表单提交验证，浏览器兼容问题

获取浏览器：

function createXmlHttp() {var xmlHttp;try { // Firefox, Opera 8.0+, SafarixmlHttp = new XMLHttpRequest();} catch (e) {try {// Internet ExplorerxmlHttp = new ActiveXObject("Msxml2.XMLHTTP");} catch (e) {try {xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");} catch (e) {}}}return xmlHttp;} 

表单提交验证：

 var xhr = createXmlHttp();            // 2.设置监听xhr.onreadystatechange = function() {if (xhr.readyState == 4) {if(xhr.status==200){var data=xhr.responseText;var success="success";var json=$.trim(data);if(success==json){document.getElementById("myform").submit();}else{alert("单位名称重复，请重新输入");return false;} }}}// 3.打开连接xhr.open("POST","TbDweckRepeat?time="+ new Date().getTime()+"&dwmc="+dwmc+"&UpdId="+id, false);// 4.发送xhr.send(null);