vue中ajax同步也无法解决对全局变量的赋值

getSchemeDetail(){
                let that = this;
                $.ajax({
                    url: 'http://**********&success_jsonpCallback=?',
                    type: 'GET',
                    data:{

                    },
                    dataType: 'JSONP',
                    jsonp:"callback",
                    jsonpCallback:"success_jsonpCallback",
                    async :false,//这里用到了同步
                    success: function (res) {
                        that.schemeDetail = res.data;//但是这里进行全局赋值还是无效
                    }
                })
            },
            ```

跪求解答~~

https://blog.csdn.net/qq_24598601/article/details/82748434

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