Table of Contents

astro

---
interface PageHeadings {
	/** The text value within the heading tag; stripped of HTML. */
	text: string;
	/** A generated slug value based on the text. */
	slug: string;
	/** Depth indicates headings H1-H6. */
	depth: number;
}

/** The generated list of page headings, slugs, and depth. */
const headings: PageHeadings[] = [
	{ text: 'Real World Example', slug: 'real-world-example', depth: 1 },
	{ text: 'Semantic Markup', slug: 'semantic-markup', depth: 1 },
	{ text: 'Utilities', slug: 'utilities', depth: 1 },
	{ text: 'Grid', slug: 'grid', depth: 2 },
	{ text: 'Alignment', slug: 'alignment', depth: 2 },
	{ text: 'Responsive Design', slug: 'responsive-design', depth: 2 },
	{ text: 'In Conclusion', slug: 'in-conclusion', depth: 1 },
];

/** Provide a padding-left class based on the depth. */
function setIndentationClass(depth: number) {
	return (
		{
			0: 'pl-0',
			1: 'pl-2',
			2: 'pl-4',
			3: 'pl-6',
			4: 'pl-8',
			5: 'pl-10',
		}[depth] ?? 'pl-0'
	);
}
---

<nav class="card bg-surface-100-900 p-4">
	<!-- Table of Contents -->
	<div class="text-sm space-y-2">
		<!-- Label -->
		<div class="font-bold">On This Page</div>
		<!-- Links -->
		<ul class="space-y-2">
			<!-- Consider a fixed scroll position at the top of your page layouts. -->
			<li><a href={`#_top`} class="anchor block">Overview</a></li>
			<!-- Loop through the available headings. -->
			{
				headings.map((heading: PageHeadings) => (
					<li>
						{/* Apply a indentation class based on the depth. */}
						<a href={`#${heading.slug}`} class="anchor block" class:list={setIndentationClass(heading.depth)}>
							{heading.text}
						</a>
					</li>
				))
			}
		</ul>
	</div>
</nav>

Deep Linking

Browsers allow you to deep link to any element via the ID. This is accomplished with an anchor tag and hashed (#) href value. When interacting with these anchors, the viewport will automatically attempt to scroll the <body> element and bring the element into view.

html

<h2 class="#some-example-slug">
	Some Example Heading
	<h2></h2>
</h2>

html

<a href="#real-world-example" class="anchor">Some Example Heading</a>

TIP: If you abstract scrolling away from the <body> element, this will not work.

Scroll Behavior

You may optionally choose to implement a smooth scroll behavior using CSS.

html

<body class="smooth-scroll"></body>

css

body {
	scroll-behavior: smooth;
}

Generate a Slug

The following provides a barebones implementation for generating a slug based on a heading text value.

function generateSlug(text: string, prefix?: string = '', suffix?: string = '') {
	// Format the slug from the text value.
	const slug = text
		.toLowerCase()
		.replaceAll(/[^a-zA-Z0-9 ]/g, '')
		.replaceAll(' ', '-')
		.toLowerCase();
	// Note that you can optionally apply a prefix/suffix.
	return `${prefix}${slug}${suffix}`;
}

// Usage
generateSlug('An Example Header'); // result: an-example-header
generateSlug('An Example Header', 'skeleton-'); // result: skeleton-an-example-header
generateSlug('An Example Header', '', '-skeleton'); // result: an-example-header-skeleton

Guides

Specific instructions for generating headings will differ based on your meta-framework and your application architecture. Below are a few suggestions, but this is neither a definitive or exhaustive list of all available options.

Astro - enables you to automatically generate headings using built-in MDX features.
Svelte - Melt UI provides a headless component solution for Svelte.
Next.js - Nextra provides a headless component solution for Next.js + MDX.
Rehype Plugin - a general purpose Rehype plugin for generating a table of contents.

catppuccin

cerberus

concord

crimson

fennec

hamlindigo

legacy

mint

modern

mona

nosh

nouveau

pine

reign

rocket

rose

sahara

seafoam

terminus

vintage

vox

wintry

Deep Linking

Scroll Behavior

Generate a Slug

Guides