SvelteKit

SvelteKit uses Vite to build, so we can use partytownVite.

1. Copy the Partytown files to the local filesystem using the Vite plugin
2. Add the Partytown script to src/routes/+layout.svelte
3. Then add 3rd party scripts
4. Optional: reverse-proxying scripts

1. Copy the Partytown files to the local filesystem using the Vite plugin

Adopting this strategy from the Partytown + Vite docs:

// vite.config.js
import { join } from 'path';
import { sveltekit } from '@sveltejs/kit/vite';
import { partytownVite } from '@builder.io/partytown/utils';

/** @type {import('vite').UserConfig} */
const config = {
  plugins: [
    sveltekit(),
    partytownVite({
      dest: join(__dirname, 'dist', '~partytown'),
    }),
  ],
};

export default config;

2. Add the Partytown script to src/routes/+layout.svelte

Adapting from the HTML integration guide

// src/routes/+layout.svelte

<script>
  import { partytownSnippet } from '@builder.io/partytown/integration'
</script>

<svelte:head>
  {@html '<script>' + partytownSnippet() + '</script>'}
</svelte:head>

3. Then add 3rd party scripts

This is where we use partytown to add those scripts (note type="text/partytown" below). If your script declares global functions or variables, make sure they are explicitly declared with window and forwarded to the web worker.

This example shows Google Tag Manager. Note window.gtag = function() instead of function gtag().

Putting it together with the previous changes, our +layout.svelte looks like:

// src/routes/+layout.svelte

<script>
	import { partytownSnippet } from '@builder.io/partytown/integration'
</script>

<slot />

<svelte:head>
	<script>
		// Forward the necessary functions to the web worker layer
		partytown = {
			forward: ['dataLayer.push', 'gtag']
		};
	</script>

	{@html '<script>' + partytownSnippet() + '</script>'}

	<script type="text/partytown" src="https://www.googletagmanager.com/gtag/js?id=G-ZX7H2KPXNZ"></script>
	<script type="text/partytown">
		window.dataLayer = window.dataLayer || [];
		window.gtag = function(){dataLayer.push(arguments);}
		gtag('js', new Date());
		gtag('config', 'G-ZX7H2KPXNZ');
	</script>
</svelte:head>

4. Optional: reverse-proxying scripts

This will only be necessary depending on which scripts you are using. The implementation will vary depending on hosting platform. See Partytown’s recommended guides.

Acknowledgements: credit belongs to monogram.io for an earlier version of this guide.