jquery ajax怎麼改變header

$.ajax({undefined
    headers: {
        Accept: "application/json; charset=utf-8"
    },
    type: "get",
    success: function (data) {
    }
});

$("#test").click(function() {
                $.ajax({
                    type: "GET",
                    url: "default.aspx",
                    beforeSend: function(request) {
                        request.setRequestHeader("Test", "Chenxizhang");
                    },
                    success: function(result) {
                        alert(result);
                    }
                });
            });