This is my front-end routing. It seems to have no problem, but when the browser refreshes locahost:4000/select/ProfessionalElective, the page will become blank. It must be entered from other routing points. I looked at the loading js and css, the paths become localhost:4000/select/js and localhost:4000/select/css. Shouldn't it be localhost:4000/js? I can directly refresh the path localhost:4000/select page and it will be displayed. What is the problem? 
The routing of my node is written like this.
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
index.html or index.jade<script src='path/to/js'></script>应该以绝对路径方式写 ,
<script src="/select/js/..."></script>inThis is about the conflict between front-end and back-end routing. Basically, when you use browserHistory, the front-end routing is not available in the back-end. When you refresh the page, the browser will request the page from the server. If the back-end does not set this route, it will naturally report 404. .
Please read the documentation for details, react-router