Sverto

Sverto is an extension for Quarto that lets you seamlessly write and include Svelte components, like charts and other visuals, in your Quarto website.
Author

James Goldie

Published

June 2, 2023

Your Svelte components can seamlessly react to your ObservableJS code, making it quick and easy to build bespoke visuals that animate in response to user inputs or other changing data in your document.

💭 Why Sverto?

Quarto helps users build beautiful documents regardless of their language of choice, and it encourages data analysts and scientists to explore web visualisation by making JavaScript accessible and easy to use. It makes interactive visualisations intuitive to write, but animated visuals are still a challenge that require either dipping into a high-level JavaScript library or learning a lower-level one like d3.

Svelte is a framework for building web visualisations and apps in JavaScript. Svelte goes out of its way to make writing self-contained components, like charts, comfortable and intuitive. It has a great playground environment for developing and testing components, but like many web frameworks, the experience is much more complex when you start developing locally.

Sverto aims to make it as easy to use animated Svelte charts in Quarto documents as it is to work on them in the Svelte REPL: just write a .svelte file, add it to a Quarto document, and Sverto should take care of the rest.

📋 Prerequisites

You’ll need to install two things to run Sverto:

⚙️ Installation

Install the project extension using:

quarto use template jimjam-slam/sverto

Then run:

npm install

This will add the extension itself (which includes some project scripts) to the _extension folder, as well as a few other files.

Note

Sverto depends on running project pre-render scripts, so you can’t currently use it with single documents.

🎉 Use

Here’s the short way to add Svelte component you’ve written to a Quarto doc:

  1. Add a magic placeholder block to your document with a Quarto include to the path to your Quarto doc, prefixed with /.sverto/. For example:

    :::{}
    {{< include /.sverto/example.qmd >}}
    :::
  2. Import your Svelte component in OJS with Component = import_svelte("Component.svelte")

  3. Add a target block for your visual using ::: and give it an #id

  4. Instantiate the Svelte component with myVisual = Component.default() using some default props and your target block

  5. Update the instantiated component with myVisual.propName

  6. Render your Quarto project as usual with quarto render or quarto preview.

To see this all in practice, check out example.qmd.

Note

The quarto preview command won’t “live reload” when you modify your Svelte component—but if you modify and save the Quarto doc that imports it, that will trigger a re-render. You may need to hard reload the page in your browser to see the updated Svelte component.

If you want to quickly iterate on the Svelte component and you aren’t too concerned about the rest of your Quarto doc, you might find the Svelte Preview extension for VSCode handy.

As well as the project format, Sverto ships with document formats (the default is sverto-html). If you need to change document options that would normally go under format: html, use format: sverto-html or format-sverto-revealjs instead.

🛍 Use other libraries in your Svelte component

If you want to refer to other JavaScript libraries in your Svelte component (like d3, for example), add them to the project using npm install package1 [package2 ...]. For example:

npm install d3-scale

🔨 Use pre-compiled Svelte components

If you’d prefer to compile your own Svelte components instead of letting this extension do it, you can skip steps 1 and 2 and simply refer to the compiled bundle with, for example, Component = import("Component.js") in an OJS block.

Note

You must compile the Svelte component to an ES6 bundle, and you must enable accessors when compiling if you want to be able to update them from OJS. Refer to _extensions/sverto/rollup.config.js for guidance on configuring Rollup to do this.

❓ Issues

If you have any problems with the extension, please feel free to create an issue!

Special thanks to Carlos Scheidegger from Posit for his time and advice!