前景:后台返回的是base64文件流。

html

 <el-button class="btn-down" type="primary" @click="downloadScoreExample">下载模板</el-button>

封装方法:
js：

  dataurlLoad(dataurl,name){
      var bstr=atob(dataurl),
      n=bstr.length,
      u8rr=new Uint8Array(n);
      while(n--){
        u8rr[n]=bstr.charCodeAt(n);
      }
      let blob = new Blob([u8rr]);
      let url=URL.createObjectURL(blob);
      let a=document.createElement('a')
      a.href=url;
      a.download=name;
      a.click();
      URL.revokeObjectURL(a.href);
     },

文件流：
例子:不带前面的 data:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;base64，

 var data = "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"

调用方法:
//res.data.file base64文件流
//res.data.name:是后台返回的文件名
this.dataurlLoad(res.data.file,res.data.name);

扩展方法:

//带data:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;base64，
//方法二
function downloadBaes64File() {
    let url = 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Md52c1StVRx8QX5K3M21xqNRrWW22KFGpD9WJnDr5VWK5vLDt6ALL46h680NpvNVQdvQBa/OodvX6qtVly8AcWMpoM5tA5ou51Ln0D6nG174WsAXyvl8CkKsmGSXVpFn6dqUa4l+A4XbQBoIMOKpkiNMtLHIaRxEyddQXGAMpxyCQOl5VK7tAJ/9W/FfKpo9Xid4MI8OxTKuSFtCZKhoJmqBx+C1KAAefX0+1dPH6NXTx8d33tyfO+n4/v3j+/9aGU5E7dxGhUnvvz2sz+/+hj98fjrlw++8ONlEf/bD588+/VzPxDqa7r+518++v3Jo+cPP33x3QMPfFPgbhHeoQmR6Do5Qvs8gbUZx7iWk64424xOjKkzA8cg2yO6pWIHeH2EmQ/XIK7zbgmgFh/w6vCOY+tBLIaKejTvxIkD3OWcNbjwOmBH6yp4uDNMI79yMSzi9jE+9Olu4tQJbWuYAadCys77vhkTx8w9hlOFI5IShfQzPiDEM+02pY5fd2kouOR9hW5T1MDU65IO7TqJNJ20TROIy8hnIITa8c3uLdTgzLfqLXLoIqEgMPMY3yHMceNVPFQ48Yns4IQVHX4Nq9hn5MFIhEVcSyqIdEQYR60ekdI354aA9RaCvoOBzbxh32WjxEUKRQc+mdcw50XkFh80Y5xkXptpGhexH8gBpChGe1z54LvcrRD9HeKA04XhvkWJE+6TieAmjRyTpgminwyFJ5ZXCXfrccT6mBiWAcJ3eDyh6etInVFg9RlSr74jdbsrzZL6JmyAvtLanqHyRbh/IYFv4WG6R6Bm5kn0HX+/4+/gP8/fi2r5/Fl7StTA4dM+3XTtycKmvU8ZO1AjRq5J07dL2J56bRg0Bwpzqpwc4rIYPuZHBAcXCWzmIMHVR1TFBzHOoMUvmyNoJHPRkUQZl9D5m2FzGiYzss3xlkJjb06qVX2GscwhsdrlPTu8UjyrTsSYk2tkzsNjRStawGmVrVx6O2Vla9VCt7lLKxvTDCk6S5ssGWI4vzQYnHgT+h4E3RJ4eRXuDLTtcBrCjPS03+05fhwWrfpcQyRj3CN5jPS652NUNkEa58o4jTwx0ufOE2JU0FbTYt9C22mCVFRXWaBuHL23idL4sD2Nkq7bmXJkabE4WYqO6kGtulwNUIizetCHYzZ8TDKIutStJmYRXFaFSti0P7GYTbpOo1nzp2UZbk6s3+cW7PBAJqTawjK2qWEe5SnAUnMpYOxfroJbz2sBNtPfwIqVNUiGv80K8KMbWtLvk1AVg10YMbciBpBTKR8qIg7i3hHqsqHYxxB+naqwnh6VcB9iGEF/gas97W3zyCXnvOiKF2oGZ8cxy2Kc060u0XElW7ip44kN5pu11pgHa/PabhZ39qWYkj+npRTT+H+2FL2fwAXFSk9HIISrZYGRrtd6wIWKObBQFtOwLeBazXAHZAtcD8NjSCq44Db/BTnU/23NWRmmrOGcqfZphASF/UjFgpA9oCWTfScIK+d7lxXJckEmowrmysya3SWHhHU0B67qvT1AMaS6YZOcBgxuNv/c73kFdSPd5PxTOx9bzGdtD3R3YFssO/+UvUilQPqFraDm3ftMTzWhg9ds7Gfcai1jza14uXrqrTaDaya4XVaQEyEVISMmjfWG2uH7wK0I3n3Y9gpBVl+wjQfSBGnpsQuNkx20yaRF2YYl727PvY2CG/K8053ohSp9k073jM6eNGeuOqcWX999ns3ZuYcdXxc7XY+roWhnS1S3R+ODjAmMec1WfBHGu3cg0FvwymHIlLQvE+7CpSKcMuxLCyh+G1wzdeMvAAAA//8DAFBLAwQUAAYACAAAACEAKlCbhAUDAACzBwAADQAAAHhsL3N0eWxlcy54bWysVc1u00AQviPxDqu9u/5JHJLINmqaWqoEElKLxHVjr5MV+2PtbkpSxI0bRx6CG+deeBsq8RjM2k5i1AKl5ZLszM5++803O+Pk+UZwdEm1YUqmODwKMKKyUCWTyxS/vsi9MUbGElkSriRN8ZYa/Dx7+iQxdsvp+YpSiwBCmhSvrK2nvm+KFRXEHKmaStiplBbEgqmXvqk1JaVxhwT3oyAY+YIwiVuEqSjuAyKIfruuvUKJmli2YJzZbYOFkSimZ0upNFlwoLoJh6TYYTfGLXjBCq2MquwRwPmqqlhBb7Oc+BMfkLKkUtIaVKi1tCkeALS7YfpWqncyd1sgYBeVJeYKXRIOnhD7WVIorjSyoAwQazySCNpG3Hz99P3bZxdVEcH4tvVGztFo2YUJBpk5p+9otGQO10zczt8wBw2VFdEGqtayGwzvd8/CsXlkSg+6vsnWQLqM8732kZMZHFkCb8BSLXMwULe+2NYgsoTn2qrVxP0leqnJNozi3gG/uTBLFkqX0B67qrsCt64s4bSyIItmy5X7t6qG34WyFt5SlpSMLJUk3FVsd6JbQDoF5fzctdCb6hfsTYXkWuTCnpUphmZ0td4tIZFu2eK1hsPvo7XYPdgBUP53WLSp9viPOI1IXfPtMWdLKahrGycg2ZlopTS7ghRdpxSwTzV208iyoudxGW6q3ycRgUx3a7NPoqXhmtQx+J+kGu1B7V5JfynovjTIdWeKb66vf3z5CLOjkxct1oxbJu8oJmCWm8PzCNzrtG62NQ9nfwu8kpJWZM3txX4zxYf1S1qytQCRuqhX7FLZBiLFh3Ub1YwRurEvDEwY+EdrzVL8/nT2bDI/zSNvHMzG3nBAY28Sz+ZePDyZzef5JIiCkw+9UfuIQdt8EKDW4XBqOIxj3SXbkT8/+FLcM164JmwGqw+0+9wn0Sg4jsPAywdB6A1HZOyNR4PYy+Mwmo+Gs9M4j3vc44dxDwM/DNuvmSMfTy0TlDO5q9WuQn0vFAnMPyThUmkq4R++ttlPAAAA//8DAFBLAwQUAAYACAAAACEAytQRq4oCAAA8BgAAGAAAAHhsL3dvcmtzaGVldHMvc2hlZXQxLnhtbKxUy27bMBC8F+g/ELxHDydxGsFykMQImkOBou7jTFOURUTksiRtx/36LilLiaMWCJpeJFIazs7O7nJ29ahashXWSdAlzZOMEqE5VFKvS/rt693JB0qcZ7piLWhR0r1w9Gr+/t1sB/bBNUJ4ggzalbTx3hRp6ngjFHMJGKHxTw1WMY9bu06dsYJV8ZBq00mWTVPFpKYdQ2FfwwF1LblYAN8ooX1HYkXLPOp3jTSuZ1P8NXSK2YeNOeGgDFKsZCv9PpJSonhxv9Zg2arFvB/zM8Z77rgZ0SvJLTiofYJ0aSd0nPNlepki03xWScwg2E6sqEt6nReLc5rOZ9Gf71Ls3LM18Wy1FK3gXlRYJkqC/SuAhwC8x08ZMroICIyMe7kVt6JtS7qYYAV/xhi4xADpEOH5uo92Fwv22ZJK1GzT+i+w+yjkuvEY9jQ5RwuCE0W1XwjHsQQYOsmjcA4tkuCTKBl6CS1kjyU9Q7Gy8g1+mSbTCTI4vw+WIoBvnAf14/A7iutYosQF82w+s7Aj2BqIdoaFRssLpAx6JvjuGAaFf5OHugLJdWDBg5TgcYeWbefZLN2iD/yAuBkj8mPE7RgxOUYsxojTAZFiPkNSoTRvTyqwRIOGpM5eJDVGnL9IqkcES/Lpn9We/he1geVY7VO4WKSbMeLihdoeEdU+pXLkLTbHG7zFOTk0XmjYf6/RMG9dM5sGb1EvOc5XDdqHycVm8XuD86DhFvThKg6jYNhafGJ2LbUjrajjpF1QYrthzBJcezBh/i5Q4wo8jlK/a/CiFdjwWYJW1QC+3xx4l8JvDDHMCLuUvzD4JSVgJc5zvElLasB6y6THeIVElfa+yuN8Dvf+/DcAAAD//wMAUEsDBBQABgAIAAAAIQCPoyYlPwEAAFECAAARAAgBZG9jUHJvcHMvY29yZS54bWwgogQBKKAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAB8kl9LwzAUxd8Fv0PJe5u20zlD24HKnhwIThTfQnLXBZs/JNFu39603WoHQ8hL7jn3d08uKZZ72UQ/YJ3QqkRZkqIIFNNcqLpEb5tVvECR81Rx2mgFJTqAQ8vq+qpghjBt4cVqA9YLcFEgKUeYKdHOe0MwdmwHkrokOFQQt9pK6sPV1thQ9kVrwHmazrEETzn1FHfA2IxEdERyNiLNt216AGcYGpCgvMNZkuE/rwcr3cWGXpk4pfAHE950jDtlczaIo3vvxGhs2zZpZ32MkD/DH+vn1/6psVDdrhigquCMMAvUa1sVeHoJi2uo8+uw460A/nAI+oUaZ33cAQI8CgHIEPekvM8enzYrVHU7jNP7OJtv0pT057MbedbfBRoK8jj4X2KexVneE3Nyc0duFxPiCTDkPv8E1S8AAAD//wMAUEsDBBQABgAIAAAAIQB/9FfuRQAAANwAAAAnAAAAeGwvcHJpbnRlclNldHRpbmdzL3ByaW50ZXJTZXR0aW5nczEuYmluYmCgDDCyMLPdARrBrM/IwMjAyTCL24QjBcjiZ4hgYgLSEUzMQNKRwYRCe5C1M0I5IJoJiEH0fyBw9wxGsQYAAAD//wMAUEsDBBQABgAIAAAAIQCFVevYmgEAABADAAAQAAgBZG9jUHJvcHMvYXBwLnhtbCCiBAEooAABAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA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    let a = document.createElement("a");             // 生成一个a元素
    let event = new MouseEvent("click");             // 创建一个单击事件
    a.download = new Date().toLocaleString();        // 设置图片名称
    a.href = url;                                    // 将生成的URL设置为a.href属性
    a.dispatchEvent(event);                          // 触发a的单击事件

简单记录一下!!! 方便查阅。