download(){
    let href  = "http://localhost:8080/download";
    const dom = document.createElement('a');
    dom.style.display = 'none';
    dom.href = href;
    document.body.appendChild(dom);
    //点击下载
    dom.click();
    //下载完成移除元素
    document.body.removeChild(dom);
},

async downloadFile(){
    const res = await axios.get("http://localhost:8080/file");

    console.log(res);

    const blob = new Blob([res.data], {type: res.headers['content-type']});
    let patt = new RegExp("filename=([^;]+\\.[^\\.;]+);*");
    let result = patt.exec(res.headers['content-disposition']);
    let filename = decodeURI(result[1]);

    const downloadElement = document.createElement('a');
    const href = window.URL.createObjectURL(blob);

    console.log(filename);
    downloadElement.style.display = 'none';
    downloadElement.href = href;
    downloadElement.download = filename ; //下载后文件名
    document.body.appendChild(downloadElement);
    downloadElement.click(); //点击下载
    document.body.removeChild(downloadElement); //下载完成移除元素
    window.URL.revokeObjectURL(href); //释放掉blob对象
}

// 设置的文件名，需要对 filename 进行转码，防止下载的文件名中有中文时出现乱码。
res.setHeader("Content-Disposition", "attachment; filename=" + encodeURI(filename));
res.setHeader("Content-Type", 'application/octet-stream');
// axios下载文件取不到content-disposition需要添加响应头
res.setHeader("Access-Control-Expose-Headers", "Content-Disposition");