Automattic

Daniel Bachhuber

Josh Betz

Add custom JavaScript to your site from an editor in the WordPress admin.
Your code is stored and revisioned with a custom post type, so you can always go back to a previous working state.
If you’d like to check out the code and contribute, <a href="https://github.com/Automattic/Custom-Javascript-Editor" rel="nofollow ugc">join us on GitHub</a>. Pull requests are more than welcome!

Custom JavaScript Editor

Add custom JavaScript to your site from an editor in the WordPress admin

WordPress.org

This plugin offloads JavaScript execution to a Web Worker, improving performance by freeing up the main thread. This should translate into improved <a href="https://web.dev/articles/inp" rel="nofollow ugc">Interaction to Next Paint</a> (INP) scores.
⚠ This functionality is experimental. ⚠
In order to opt in a script to be loaded in a worker, simply add <code>worker</code> script data to a registered script. For example, 
if you have a script registered with the handle of <code>foo</code>, opt-in to offload it to a web worker by doing:
<pre><code>wp_script_add_data( 'foo', 'worker', true );
</code></pre>
Unlike with the script loading strategies (async/defer), any inline before/after scripts associated with the worker-offloaded registered script will also be offloaded to the worker, whereas with the script strategies an inline after script would block the script from being delayed.
Otherwise, the plugin currently ships with built-in integrations to offload Google Analytics to a web worker for the following plugin:
<ul>
<li><a href="https://wordpress.org/plugins/seo-by-rank-math/" rel="ugc">Rank Math SEO</a></li>
<li><a href="https://wordpress.org/plugins/google-site-kit/" rel="ugc">Site Kit by Google</a></li>
<li><a href="https://wordpress.org/plugins/woocommerce/" rel="ugc">WooCommerce</a></li>
</ul>
Please monitor your analytics once activating to ensure all the expected events are being logged. At the same time, monitor your INP scores to check for improvement.
This plugin relies on the <a href="https://partytown.builder.io/" rel="nofollow ugc">Partytown 🎉</a> library by Builder.io, released under the MIT license. This library is in beta and there are quite a few <a href="https://github.com/BuilderIO/partytown/issues?q=is%3Aopen+is%3Aissue+label%3Abug" rel="nofollow ugc">open bugs</a>.
The <a href="https://partytown.builder.io/configuration" rel="nofollow ugc">Partytown configuration</a> can be modified via the <code>plwwo_configuration</code> filter. For example:
<pre><code><?php
add_filter( 'plwwo_configuration', function ( $config ) {
 $config['mainWindowAccessors'][] = 'wp'; // Make the wp global available in the worker (e.g. wp.i18n and wp.hooks).
 return $config;
} );
</code></pre>
However, not all of the configuration options can be serialized to JSON in this way, for example the <code>resolveUrl</code> configuration is a function. To specify this, you can add an inline script as follows.
<pre><code><?php
add_action(
 'wp_enqueue_scripts',
 function () {
 wp_add_inline_script(
 'web-worker-offloading',
 <<<JS
 window.partytown = {
 ...(window.partytown || {}),
 resolveUrl: (url, location, type) => {
 if (type === 'script') {
 const proxyUrl = new URL('https://my-reverse-proxy.example.com/');
 proxyUrl.searchParams.append('url', url.href);
 return proxyUrl;
 }
 return url;
 },
 };
 JS,
 'before'
 );
 }
);
</code></pre>
There are also many configuration options which are not documented, so refer to the <a href="https://github.com/BuilderIO/partytown/blob/b292a14047a0c12ca05ba97df1833935d42fdb66/src/lib/types.ts#L393-L548" rel="nofollow ugc">TypeScript definitions</a>.

Web Worker Offloading

Offloads select JavaScript execution to a Web Worker to reduce work on the main thread and improve the Interaction to Next Paint (INP) metric.

Custom JavaScript Editor vs Web Worker Offloading