js vue 导出文件 判断json报错

     // 环境 vue
      let query = {};
      query.export = 1;
      this.loading = true;
      request({
        url: "xxx/xxxxx/xxxx",
        method: "get",
        params: query,
        responseType: "blob",
      })
        .then((response) => {
          this.loading = false;
          const data = response;
          if (!data) {
            return;
          }
          const f = new FileReader();
          let that = this
          f.onload = function () {
            try {
              let res = JSON.parse(this.result);
              that.$message.error(res.message);
            } catch (err) {
              let url = window.URL.createObjectURL(new Blob([data]));
              let link = document.createElement("a");
              link.style.display = "none";
              link.href = url;
              const date = new Date();

              link.setAttribute(
                "download",
                "xxxx" +
                  date.toLocaleDateString() +
                  " " +
                  date.toLocaleTimeString() +
                  ".xls"
              );
              document.body.appendChild(link);
              link.click();
            }
          };
          f.readAsText(data);
          return;
        })
        .finally(() => {
          this.loading = false;
        });