valid json request body in jquery json

valid json request body in jquery json

    var uid= "user";
    var pwd= "user@123";

    var doAuthenticate = function (uid, pwd) {
        var token = user + ':' + password;
        var hashCode = btoa(token);
        return  'Basic ' + hashCode; 
    };

    var createDate = new Date().getTime();

    var requestBody = { user: { Id: 9, CreatedDate: '/Date(' + createDate + ')/'} };
    var JSONrequestBody=JSON.stringify(requestBody);

        $.ajax({
            url: 'http://aspdotnetblogspot.blogspot.in/2013/06/authentication-on-wcf-rest-service-json.html',
            type: 'POST',
            data: JSONrequestBody,
            beforeSend: function (xhr) {
                xhr.setRequestHeader("Authorization", doAuthenticate(uid, pwd));
            },
            async: runInBackground,
            contentType: 'application/json',
            success: successHandler,
            error: function (jqXHR, textStatus, errorThrown) {
                   $('#msgText').html(jqXHR.responseText);

            }
        });

Thanks you.