axios请求设置responseType为'blob'或'arraybuffer'下载时如何正确处理返回值

responseType: 'arraybuffer'

return 'data:image/png;base64,' + btoa(
    new Uint8Array(res.data).reduce((data, byte) => data + String.fromCharCode(byte), '')
  );

axios.post( ExportUrl, Params, {
    responseType: 'blob'
  })
  .then(function(response) {
    this.url = window.URL.createObjectURL(new Blob([response.data]));
    
  });

const url = '下载的url链接';
const link = document.createElement('a');
link.href = url;
link.target = '_blank';
link.setAttribute('download', 'Excel名字.xlsx');
document.body.appendChild(link);
link.click();

async downloadFile (file) {
      let res = await this.$axios.post(this.API.order.tradeImpExcle, { responseType: "arraybuffer" });
      if (!res) return;
      try {
        //如果JSON.parse(enc.decode(new Uint8Array(res.data)))不报错，说明后台返回的是json对象，则弹框提示
        //如果JSON.parse(enc.decode(new Uint8Array(res.data)))报错，说明返回的是文件流，进入catch，下载文件
        let enc = new TextDecoder('utf-8')
        res = JSON.parse(enc.decode(new Uint8Array(res.data))) //转化成json对象
        if (res.Status == "true") {
          this.refresh()
          this.$message.success(res.Msg)
        } else {
          this.$message.error(res.Result)
        }
      } catch (err) {
        const content = res.data;
        const blob = new Blob([content]);
        let url = window.URL.createObjectURL(blob);
        let link = document.createElement("a");
        link.style.display = "none";
        link.href = url;
        link.setAttribute(
          "download",
          res.headers["content-disposition"].split("=")[1]
        );
        document.body.appendChild(link);
        link.click();
      }
    }

 async downloadFile (file) {
      let formData = new FormData();
      formData.append("allTradesExcelFile", file);
      let res = await this.$axios.post(this.API.order.tradeImpExcle, formData, { responseType: "blob" });
      if (!res) return;
      let r = new FileReader()
      let _this = this
      r.onload = function () {
        try {
          // 如果JSON.parse(this.result)不报错，说明this.result是json对象，则弹框提示
          // 如果JSON.parse(this.result)报错，说明返回的是文件流，进入catch，下载文件
          res = JSON.parse(this.result)
          if (res.Status == "true") {
            _this.refresh()
            _this.$message.success(res.Msg)
          } else {
            _this.$message.error(res.Result)
          }
        } catch (err) {
          const content = res.data;
          const blob = new Blob([content]);
          let url = window.URL.createObjectURL(blob);
          let link = document.createElement("a");
          link.style.display = "none";
          link.href = url;
          link.setAttribute(
            "download",
            res.headers["content-disposition"].split("=")[1]
          );
          document.body.appendChild(link);
          link.click();
        }
      }
      r.readAsText(res.data) // FileReader的API
    }