download(url, fileName ) {
      let self = this;
      const url = url
      let x = new XMLHttpRequest();
      x.open("GET", url, true);
      x.responseType = "blob";
      x.onload = function() {
        //self.exportLoading = false;
        let url = window.URL.createObjectURL(x.response);
        let a = document.createElement("a");
        a.href = url;
        a.download = fileName;
        a.click();
      };
      x.send();
    }

在页面这样使用
download(url, ’文件名字‘)