Ajax中传递Json格式的参数

$.ajax({
 type: "post",
 url: baseUrl+"sys/login",
 dataType: "json",
 contentType: "application/json;charset=utf-8",
 data: JSON.stringify({userName: loginapp.userName,userPassword: loginapp.userPassword}),
　　
 或者拼接字符串的形式：
 data: "{'userName': '"+loginapp.userName+"','userPassword': '"+loginapp.userPassword+"'}",