let name = res.headers["content-disposition"].split(';')[1].split('filename=')[1];
js模拟a标签下载blob
downloadFileByBlob(content, fileName) {
const blob = new Blob([content]);
const a = document.createElement("a");
const url = window.URL.createObjectURL(blob);
const filename = fileName;
a.href = url;
a.download = filename;
a.click();
window.URL.revokeObjectURL(url);
}