思源学堂更新后，PDF竟然只能在线预览，无法下载至本地！！
经过网页源码分析，解决此问题非常简单。主要分为以下几个步骤：
- 来到PDF预览界面，进入开发者面板（F12键），全局搜索（ctrl+shift+f）
domainName"关键字（注意最后还有个引号，方便更好的找到） - 选择
arg-script.js这个选项，可以看到如下字样：
"domainName":"https://lms.xjtu.edu.cn/note-bene/pdf-viewer?file=https%3A%2F%2Fmedia.xjtu.edu.cn%3A443%2Fdownload%2Ffile%2F08fc9d4ea8002f5d56c918dcd4967e10ee21a7fa%3Ftimestamp%3D1757779200%26token%3D38441fe4cd851dbf8eba86e4c30fa5a7%26name%3D%25E7%2594%25B5%25E9%2598%25BB%25E7%259A%2584%25E6%2598%259F%25E5%25BD%25A2%25E8%2581%2594%25E7%25BB%2593%25E5%2592%258C%25E4%25B8%2589%25E8%25A7%2592%25E5%25BD%25A2%25E8%2581%2594%25E7%25BB%2593%25E7%259A%2584%25E7%25AD%2589%25E6%2595%2588%25E5%258F%2598%25E6%258D%25A2.pdf&upload_id=64191&is_attachment_view=false&course_id=21462"
- 上述字样包含下载地址的url编码形式（实际下载地址从
https开始到.pdf结束），同样利用url编码方式解码即可。解码方式仅提供两种参考：
（1）利用js内置解码函数
//注意用反引号（``）将3中的复制字样括起来
decodeURIComponent(`https://lms.xjtu.edu.cn/note-bene/pdf-viewer?file=https%3A%2F%2Fmedia.xjtu.edu.cn%3A443%2Fdownload%2Ffile%2F08fc9d4ea8002f5d56c918dcd4967e10ee21a7fa%3Ftimestamp%3D1757779200%26token%3D38441fe4cd851dbf8eba86e4c30fa5a7%26name%3D%25E7%2594%25B5%25E9%2598%25BB%25E7%259A%2584%25E6%2598%259F%25E5%25BD%25A2%25E8%2581%2594%25E7%25BB%2593%25E5%2592%258C%25E4%25B8%2589%25E8%25A7%2592%25E5%25BD%25A2%25E8%2581%2594%25E7%25BB%2593%25E7%259A%2584%25E7%25AD%2589%25E6%2595%2588%25E5%258F%2598%25E6%258D%25A2.pdf&upload_id=64191&is_attachment_view=false&course_id=21462`)
将字符串用反引号括起来，传入decodeURIComponent函数，在控制台即可输出结果。
（2）利用在线解码工具，例如：解码工具
5. 解码后格式类似如下：
https://lms.xjtu.edu.cn/note-bene/pdf-viewer?file=https://media.xjtu.edu.cn:443/download/file/08fc9d4ea8002f5d56c918dcd4967e10ee21a7fa?timestamp=1757779200&token=38441fe4cd851dbf8eba86e4c30fa5a7&name=%E7%94%B5%E9%98%BB%E7%9A%84%E6%98%9F%E5%BD%A2%E8%81%94%E7%BB%93%E5%92%8C%E4%B8%89%E8%A7%92%E5%BD%A2%E8%81%94%E7%BB%93%E7%9A%84%E7%AD%89%E6%95%88%E5%8F%98%E6%8D%A2.pdf&upload_id=64191&is_attachment_view=false&course_id=21462
从file=后面开始复制到.pdf结束即为pdf下载地址，输入网址栏回车即可。此例中即为：
https://media.xjtu.edu.cn:443/download/file/08fc9d4ea8002f5d56c918dcd4967e10ee21a7fa?timestamp=1757779200&token=38441fe4cd851dbf8eba86e4c30fa5a7&name=%E7%94%B5%E9%98%BB%E7%9A%84%E6%98%9F%E5%BD%A2%E8%81%94%E7%BB%93%E5%92%8C%E4%B8%89%E8%A7%92%E5%BD%A2%E8%81%94%E7%BB%93%E7%9A%84%E7%AD%89%E6%95%88%E5%8F%98%E6%8D%A2.pdf