Add a demo link to TypeScript code blocks

🌱May 9, 2024.
seedling 🌱
3 minutes read ⏱

TypeScript Playground is an online tool to interactive with TypeScript. It’s a great way to test out small snippets, share repros, and experiment with the language as it is portable and requires no setup. Recently, I learned about another amazing feature - it’s possible to Dynamically generate TypeScript Playground links for any TypeScript code! Technical writing should Make example code interactive, and this is an excellent way to do it.

Once I’ve got my TS playground link generated, all that’s left is to put the link on the page. Easy!

I already built a copy button for my code blocks, which makes this even easier. I modified that code to render TS playground links instead of copy buttons. This Svelte component renders a link as a small square button:

<script lang="ts">
	import { Icon } from '@steeze-ui/svelte-icon';
	import { ArrowTopRightOnSquare } from '@steeze-ui/heroicons';

	export let href: string;

	const tailwindClasses = 
		"group flex items-center rounded-lg border " +
		"border-base-content/50 px-3 py-2 " +
		"hover:border-base-content transition-all "
	// Reactively add any classes passed to the component
	// This allows component consumers to style the link
	$: classes = tailwindClasses + $$props.class

	title="Open in TypeScript playground"
		class="w-6 stroke-base-content/50 transition-colors group-hover:stroke-base-content" />
	<span class="sr-only">Open this code snippet on typescript playground</span>

Great! But I still need to find the <pre> tags with a data-tsplay attribute and use my new component with them. I only need this to happen on pages based on markdown and rendered using MDSveX, so I put the logic in my mdsvex layout component.

For these links to show up on my code blocks, I need to:

  1. Find all the code block elements (<pre> tags) with a data-tsplay attribute
  2. Grab the TS playground link from the data-tsplay attribute
  3. Instantiate a TSPlaygroundButton with the link and put it on the code block

1 & 2 are pretty straightforward with basic browser APIs. I’m using svelte, so I did number 3 with the Svelte client-side component API. It should be pretty similar in other frameworks.

	import { onMount } from 'svelte';
	import { default as TSPlaygroundButton } from '$lib/components/TSPlaygroundButton.svelte';

	function addTSPlaygroundLinkToCodeBlocks() {
		// 1. Find all the code block elements with a playground link
		const codeblocks = document.querySelectorAll(
		Array.from(codeblocks).forEach((element) => {
			// 2. grab the playground link
			const tsplaylink = element.getAttribute('data-tsplay');
			if (!tsplaylink) { return; }
			const anchor = element.firstElementChild;
			if (!anchor) return;
			// 3. instantiate the button using the 
			new TSPlaygroundButton({
				target: element,
				props: {
					href: tsplaylink,
					// This positions the link left of the copy button
					class: 'absolute top-2 right-16'
	// Once the page is mounted add the TS playground links
	onMount(() => {

<slot />

Adding these interactive links is how I Make example code interactive on my blog. I built it for a SeattleJS presentation on Branded Types that I ran out of that very blog post! It turned out to be a valuable tool for quick demos when I wanted to do live coding or show runtime outputs.