hexo-theme-icarus/layout/_partial/cdn_after_footer.ejs

<% if (theme.cdn == "useso"){ %>
 <script src="//ajax.useso.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<% } else if (theme.cdn == "ustc") { %>
 <script src="//ajax.lug.ustc.edu.cn/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<% } else { %>
 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<% } %>