jQuery Ajax表单提交错误处理

I have the following code:

我有以下代码:

var url = "save.php"; // the script where you handle the form input.   

$.ajax({
        type: "POST",
        url: url,
        data: $("#frmSurvey").serialize(), // serializes the form's elements.

        success: function(){
            alert('success');
          },
        error: function(){
            alert( "Request failed: " );
          }

        }); 
var url