vue-resource中使用jsonp，参数不全

使用vue+vue-resource发送jsonp请求：

var jsonStr = {
                "userId":"",
                "type":this.type,
                "name":this.searchContent,
                "itId" : this.itId,
                "regionid" : this.regionid=="0"?"":this.regionid,
                "pageNow":this.pageNum,
                "sort":"",
                "pageCount":"10",
                "auditstatus":"2"
            };
            jsonStr = JSON.stringify(jsonStr);
            var sendData = {
                marked : "helpList",
                jsonStr : jsonStr
            };
            var that = this;

/*            var _fnCallback_needmarket = function(data) {
                //window.demo.h5Log(JSON.stringify(data)); 
                that.helpList = that.helpList.concat(data.helpList);
            };*/

            console.log(sendData);

            this.$http.jsonp(Util.url,{
                params : sendData
            }).then((response) => {
                // success callback
                that.helpList = that.helpList.concat(response.helpList);
            }, (response) => {
                // error callback
            });

发送之前console.log了一下，sendData的值是

但是发送请求的时候，看请求里，参数不全，如下

没有了mark字段和callback字段。谁能告诉我下为什么？