.eleventy.js

const fs = require("fs");
const path = require("path");

const markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");
const markdownItLinkAttributes = require("markdown-it-link-attributes");

const syntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
const tableOfContents = require("eleventy-plugin-toc");

const katex = require("katex");
const yaml = require("js-yaml");

module.exports = function (eleventyConfig) {
  // This will copy these folders to the output without modifying them at all
  eleventyConfig.addPassthroughCopy("js");
  eleventyConfig.addPassthroughCopy("img");
  eleventyConfig.addPassthroughCopy("css");
  eleventyConfig.addPassthroughCopy("_redirects");

  // handle LaTeX
  eleventyConfig.addFilter("latex", (content) => {
    return content.replace(/\$\$(.+?)\$\$/g, (_, equation) => {
      const cleanEquation = equation
        .replace(/&lt;/g, "<")
        .replace(/&gt;/g, ">");

      return katex.renderToString(cleanEquation, { throwOnError: true });
    });
  });

  // add markdown header anchors and a table of contents
  let markdown = markdownIt({
    html: true,
    breaks: true,
    linkify: true,
  })
    .use(markdownItAnchor)
    .use(markdownItLinkAttributes, [
      {
        pattern: /^(?!(\/|#)).*$/gm,
        attrs: {
          target: "_blank",
          rel: "noopener",
        },
      },
    ]);

  eleventyConfig.setLibrary("md", markdown);

  // enable plugins
  eleventyConfig.addPlugin(syntaxHighlight);
  eleventyConfig.addPlugin(tableOfContents);

  return {
    markdownTemplateEngine: "njk",
    jsDataFileSuffix: ".data",
    dir: {
      layouts: "_includes/layouts",
    },
  };
};