README.md

@@ -31,7 +31,7 @@ I wanted it to be nearly as feature-rich as popular blogging templates like [bea
 
 - Easy styling customization with [Tailwind 2.0](https://blog.tailwindcss.com/tailwindcss-v2) and primary color attribute
 - Near perfect lighthouse score - [Lighthouse report](https://www.webpagetest.org/result/210111_DiC1_08f3670c3430bf4a9b76fc3b927716c5/)
-- Lightweight, 38kB first load JS, uses Preact in production build
+- Lightweight, 39kB first load JS, uses Preact in production build
 - Mobile-friendly view
 - Light and dark theme
 - Supports [plausible](https://plausible.io/), [simple analytics](https://simpleanalytics.com/) and google analytics
@@ -43,6 +43,7 @@ I wanted it to be nearly as feature-rich as popular blogging templates like [bea
 - Support for tags - each unique tag will be its own page
 - Support for multiple authors
 - Blog templates
+- TOC component
 - Support for nested routing of blog posts
 - Supports [giscus](https://github.com/laymonage/giscus), [utterances](https://github.com/utterance/utterances) or disqus
 - Projects page

components/MDXComponents.js

@@ -3,10 +3,12 @@ import { useMemo } from 'react'
 import { getMDXComponent } from 'mdx-bundler/client'
 import Image from './Image'
 import CustomLink from './Link'
+import TOCInline from './TOCInline'
 import Pre from './Pre'
 
 export const MDXComponents = {
   Image,
+  TOCInline,
   a: CustomLink,
   pre: Pre,
   wrapper: ({ components, layout, ...rest }) => {

components/TOCInline.js

@@ -0,0 +1,64 @@
+/**
+ * @typedef TocHeading
+ * @prop {string} value
+ * @prop {number} depth
+ * @prop {string} url
+ */
+
+/**
+ * Generates an inline table of contents
+ * Exclude titles matching this string (new RegExp('^(' + string + ')$', 'i')).
+ * If an array is passed the array gets joined with a pipe (new RegExp('^(' + array.join('|') + ')$', 'i')).
+ *
+ * @param {{
+ *  toc: TocHeading[],
+ *  indentDepth?: number,
+ *  fromHeading?: number,
+ *  toHeading?: number,
+ *  asDisclosure?: boolean,
+ *  exclude?: string|string[]
+ * }} props
+ *
+ */
+const TOCInline = ({
+  toc,
+  indentDepth = 3,
+  fromHeading = 1,
+  toHeading = 6,
+  asDisclosure = false,
+  exclude = '',
+}) => {
+  const re = Array.isArray(exclude)
+    ? new RegExp('^(' + exclude.join('|') + ')$', 'i')
+    : new RegExp('^(' + exclude + ')$', 'i')
+
+  const filteredToc = toc.filter(
+    (heading) =>
+      heading.depth >= fromHeading && heading.depth <= toHeading ** !re.test(heading.value)
+  )
+
+  const tocList = (
+    <ul>
+      {filteredToc.map((heading) => (
+        <li key={heading.value} className={`${heading.depth >= indentDepth && 'ml-6'}`}>
+          <a href={heading.url}>{heading.value}</a>
+        </li>
+      ))}
+    </ul>
+  )
+
+  return (
+    <>
+      {asDisclosure ? (
+        <details open>
+          <summary className="pt-2 pb-2 ml-6 text-xl font-bold">Table of Contents</summary>
+          <div className="ml-6">{tocList}</div>
+        </details>
+      ) : (
+        tocList
+      )}
+    </>
+  )
+}
+
+export default TOCInline

data/blog/introducing-tailwind-nextjs-starter-blog.mdx

@@ -1,7 +1,7 @@
 ---
 title: 'Introducing Tailwind Nextjs Starter Blog'
 date: '2021-01-12'
-lastmod: '2021-08-02'
+lastmod: '2021-08-07'
 tags: ['next-js', 'tailwind', 'guide']
 draft: false
 summary: 'Looking for a performant, out of the box template, with all the best in web technology to support your blogging needs? Checkout the Tailwind Nextjs Starter Blog template.'
@@ -36,7 +36,7 @@ I wanted it to be nearly as feature-rich as popular blogging templates like [bea
 
 - Easy styling customization with [Tailwind 2.0](https://blog.tailwindcss.com/tailwindcss-v2) and primary color attribute
 - Near perfect lighthouse score - [Lighthouse report](https://www.webpagetest.org/result/210111_DiC1_08f3670c3430bf4a9b76fc3b927716c5/)
-- Lightweight, 38kB first load JS, uses Preact in production build
+- Lightweight, 39kB first load JS, uses Preact in production build
 - Mobile-friendly view
 - Light and dark theme
 - Supports [plausible](https://plausible.io/), [simple analytics](https://simpleanalytics.com/) and google analytics
@@ -48,6 +48,7 @@ I wanted it to be nearly as feature-rich as popular blogging templates like [bea
 - Support for tags - each unique tag will be its own page
 - Support for multiple authors
 - Blog templates
+- TOC component
 - Support for nested routing of blog posts
 - Supports [giscus](https://github.com/laymonage/giscus), [utterances](https://github.com/utterance/utterances) or disqus
 - Projects page

data/blog/new-features-in-v1.mdx

@@ -1,6 +1,6 @@
 ---
 title: 'New features in v1'
-date: 2021-07-28T15:32:14Z
+date: 2021-08-07T15:32:14Z
 tags: ['next-js', 'tailwind', 'guide']
 draft: false
 summary: 'An overview of the new features released in v1 - code block copy, multiple authors, frontmatter layout and more'
@@ -11,16 +11,9 @@ layout: PostSimple
 
 A post on the new features introduced in v1.0. New features:
 
-- [Theme colors](#theme-colors)
+<TOCInline toc={props.toc} exclude="Overview" toHeading={2} />
-- [Xdm MDX compiler](#xdm-mdx-compiler)
-- [Layouts](#layouts)
-- [Multiple authors](#multiple-authors)
-- [Analytics](#analytics)
-- [Blog comments system](#blog-comments-system)
-- [Copy button for code blocks](#copy-button-for-code-blocks)
-- [Line highlighting and line numbers](#line-highlighting-and-line-numbers)
 
-First load JS decreased from 43kB to 38kB despite all the new features added!
+First load JS decreased from 43kB to 39kB despite all the new features added!
 
 See [upgrade guide](#upgrade-guide) below if you are migrating from v0 version of the template.
 
@@ -75,6 +68,30 @@ Components which require external image loaders would require additional esbuild
 Components which are dependent on global application state on lifecycle like the Nextjs `Link` component would also not work with this setup as each mdx file is built indepedently.
 For such cases, it is better to use component substitution.
 
+## Table of contents component
+
+Inspired by [Docusaurus](https://docusaurus.io/docs/next/markdown-features/inline-toc) and Gatsby's [gatsby-remark-table-of-contents](https://www.gatsbyjs.com/plugins/gatsby-remark-table-of-contents/),
+the `toc` variable containing all the top level headings of the document is passed to the MDX file and can be styled accordingly.
+To make generating a TOC simple, you can use the existing `TOCInline` component.
+
+For example, the TOC in this post was generated with the following code:
+
+```js
+<TOCInline toc={props.toc} exclude="Overview" toHeading={2} />
+```
+
+You can customise the headings to be generated by configuring the `fromHeading` and `toHeading` props as well as exclude particular headings
+by passing a string or a string array. By default, all headings that are of depth 3 or smaller are indented. This can be configured by changing the `indentDepth` property.
+A `asDisclosure` prop can be used to render the TOC within an expandable disclosure element.
+
+Here's the full TOC rendered in a disclosure element.
+
+```js
+<TOCInline toc={props.toc} asDisclosure />
+```
+
+<TOCInline toc={props.toc} asDisclosure />
+
 ## Layouts
 
 You can map mdx blog content to layout components by configuring the frontmatter field. For example, this post is written with the new `PostSimple` layout!

lib/mdx.js

@@ -5,6 +5,7 @@ import path from 'path'
 import readingTime from 'reading-time'
 import visit from 'unist-util-visit'
 import codeTitles from './remark-code-title'
+import remarkTocHeadings from './remark-toc-headings'
 import imgToJsx from './img-to-jsx'
 import getAllFilesRecursively from './utils/files'
 
@@ -66,6 +67,8 @@ export async function getFileBySlug(type, slug) {
     )
   }
 
+  let toc = []
+
   const { frontmatter, code } = await bundleMDX(source, {
     // mdx imports can be automatically source from the components directory
     cwd: path.join(process.cwd(), 'components'),
@@ -77,6 +80,7 @@ export async function getFileBySlug(type, slug) {
         ...(options.remarkPlugins ?? []),
         require('remark-slug'),
         require('remark-autolink-headings'),
+        [remarkTocHeadings, { exportRef: toc }],
         require('remark-gfm'),
         codeTitles,
         [require('remark-footnotes'), { inlineNotes: true }],
@@ -111,6 +115,7 @@ export async function getFileBySlug(type, slug) {
 
   return {
     mdxSource: code,
+    toc,
     frontMatter: {
       readingTime: readingTime(code),
       slug: slug || null,

lib/remark-toc-headings.js

@@ -0,0 +1,12 @@
+import visit from 'unist-util-visit'
+
+module.exports = function (options) {
+  return (tree) =>
+    visit(tree, 'heading', (node, index, parent) => {
+      options.exportRef.push({
+        value: node.children[1].value,
+        url: node.children[0].url,
+        depth: node.depth,
+      })
+    })
+}

pages/blog/[...slug].js

@@ -39,13 +39,14 @@ export async function getStaticProps({ params }) {
 }
 
 export default function Blog({ post, authorDetails, prev, next }) {
-  const { mdxSource, frontMatter } = post
+  const { mdxSource, toc, frontMatter } = post
 
   return (
     <>
       {frontMatter.draft !== true ? (
         <MDXLayoutRenderer
           layout={frontMatter.layout || DEFAULT_LAYOUT}
+          toc={toc}
           mdxSource={mdxSource}
           frontMatter={frontMatter}
           authorDetails={authorDetails}

tailwind.config.js

@@ -74,6 +74,14 @@ module.exports = {
             'code:after': {
               content: 'none',
             },
+            details: {
+              backgroundColor: theme('colors.gray.100'),
+              paddingLeft: '4px',
+              paddingRight: '4px',
+              paddingTop: '2px',
+              paddingBottom: '2px',
+              borderRadius: '0.25rem',
+            },
             hr: { borderColor: theme('colors.gray.200') },
             'ol li:before': {
               fontWeight: '600',
@@ -119,6 +127,9 @@ module.exports = {
             code: {
               backgroundColor: theme('colors.gray.800'),
             },
+            details: {
+              backgroundColor: theme('colors.gray.800'),
+            },
             hr: { borderColor: theme('colors.gray.700') },
             'ol li:before': {
               fontWeight: '600',