function post(url,data,success){
    data = JSON.stringify(data);

    var xmlhttp = null;
    if(window.XMLHttpRequest){
        xmlhttp = new XMLHttpRequest();
    }
    xmlhttp.open("POST",url,true);
    xmlhttp.setRequestHeader("Content-type", "application/json;charset=UTF-8");//www-form-urlencoded        
    xmlhttp.overrideMimeType('audio/wav');
    xmlhttp.responseType = "blob";
    xmlhttp.timeout = 30000;
    xmlhttp.onreadystatechange = function () { 
                if (xmlhttp.readyState == 4) {
                    if (xmlhttp.status == 504 ) {
                        console.log("服务器请求超时..");
                        error();
                        xmlhttp.abort();
                    }else if(xmlhttp.status == 200){
                        // console.log(typeof xmlhttp.response);
                        success(xmlhttp);  
                    }
                    xmlhttp = null;
                }
            }
    xmlhttp.ontimeout = function () {
        console.log("客户端请求超时..");
        error();
    }
    xmlhttp.send(data);
    
    
    // timeout
    function error(){
        alert('连接超时，请刷新重试！')
    }
}