Ajax 调用案例及错误捕捉

1、ajax调用案例（拷贝）

        $.ajax({
            type: "post", dataType: "json", async: true, cache: true,
            url: "/testServlet", data: {"id": ""},
            success: function (data) {
                console.log("data", data);
            },
            error: function (err) {
                console.log("error", err);
            }
        });

2、代码

function f4() {
        var config = {
            type: "post", dataType: "json",
            url: "/testServlet",
            data: {"id": ""},
            success: function (data) {
                console.log("后台返回数据", data);
            }
        };
        $.ajax(config);
    }

    function f5() {
        $.ajax({
            type: "post", dataType: "json", async: true, cache: true,
            url: "/testServlet",
            data: {"id": ""},
            success: function (data) {
                console.log("后台返回数据", data);
            }
        });
    }

3、还是代码

function postFunc() {
            var scoreResultStr = readyData();
            $.ajax({
                type: "post",
                url: "/Score/AddScore",
                data: {
                    userId: $("#userId").val(), sessionId: $("#sessionId").val(), hallId: $("#smallMeetingId").val(), mid: $("#mid").val(),
                    scoreResultData: scoreResultStr, remark: $("#remark").val()
                },
                success: function (obj) {
                    if (obj.code == "200") {
                        layer.msg('评价成功！', { icon: 1, time: 1800 });
                    }
                    else {
                        layer.msg(obj.message, { icon: 7, time: 1800 });
                    }
                },
                error: function (XMLHttpResponse, textStatus, errorThrown) {
                    console.log("1 异步调用返回失败,XMLHttpResponse.readyState:" + XMLHttpResponse.readyState);
                    console.log("2 异步调用返回失败,XMLHttpResponse.status:" + XMLHttpResponse.status);
                    console.log("3 异步调用返回失败,textStatus:" + textStatus);
                    console.log("4 异步调用返回失败,errorThrown:" + errorThrown);
                }
                //error: function () { layer.msg('发生错误，请联系客服！', { icon: 2, time: 1800 }); }
            });
        }

{"result":{"142":"头颈科专题上","143":"头颈科专题下"},"message":"操作成功","code":200}

{"result":{},"message":"未将对象引用设置到对象的实例。","code":500}