hexo/node_modules/hexo-theme-fluid/layout/_partials/plugins/math.ejs

<% if(theme.post.math.engine === 'mathjax') { %>
  <%
    var lazy = theme.lazyload.enable && require_version(theme.static_prefix.mathjax, '3.2.0')

    import_script(`
      <script>
        if (!window.MathJax) {
          window.MathJax = {
            tex    : {
              inlineMath: { '[+]': [['$', '$']] }
            },
            loader : {
              ${ lazy ? 'load: \[\'ui/lazy\'\]' : '' }
            },
            options: {
              renderActions: {
                insertedScript: [200, () => {
                  document.querySelectorAll('mjx-container').forEach(node => {
                    let target = node.parentNode;
                    if (target.nodeName.toLowerCase() === 'li') {
                      target.parentNode.classList.add('has-jax');
                    }
                  });
                }, '', false]
              }
            }
          };
        } else {
          MathJax.startup.document.state(0);
          MathJax.texReset();
          MathJax.typeset();
          MathJax.typesetPromise();
        }

        Fluid.events.registerRefreshCallback(function() {
          if ('MathJax' in window && MathJax.startup.document && typeof MathJax.startup.document.state === 'function') {
            MathJax.startup.document.state(0);
            MathJax.texReset();
            MathJax.typeset();
            MathJax.typesetPromise();
          }
        });
      </script>
    `)

    import_js(theme.static_prefix.mathjax.replace('es5/', ''), 'es5/tex-mml-chtml.js')
  %>

<% } else if (theme.post.math.engine === 'katex') { %>
  <% import_css(theme.static_prefix.katex, 'katex.min.css') %>
<% } %>