Running scripts injected by GTM without a url on main thread

There is a script that is loaded using google tag manager that we would like to run on a main thread, while keeping other scripts working using partytown.

To load it a script is injected into the html that sets a config property on window and then creates a new <script> tag with a url. I’ve added the url of the script to loadScriptsOnMainThread and the script that is loaded from the url is working on the main thread, which is what we want, but the first script, directly injected by gtm, is still created with text/partytown.

So the problem is that for the second script with url to work, the first script needs to set config on window, which it sets in the web worker, and the script that is ran on the main thread does not have access to it.

So my question is if there is a way to run a single script (without a url) injected by gtm on the main thread?

The first script basically does this:

window.lib_config = {/* some config in here */};
var a = f.createElement("script");
a.async = !0;
a.type = "text/javascript";
a.src = /* lib url */;
f.head.appendChild(a);

[michaelbourne]

@teunissenstefan it appears to only work via URL, not ID like documented. I still haven’t found the cause of the error, typescript isn’t my forte.

It looks like this line is only checking the URL of scripts, not the ID: https://github.com/BuilderIO/partytown/blob/main/src/lib/web-worker/worker-script.ts#L30

Partytown.j grabs script elements with https://developer.mozilla.org/en-US/docs/Web/API/HTMLScriptElement and HTMLScriptElement inherits properties from Element, so id is available as a property.

It seems like we need to amend that check to something along the lines of this, but I’m not sure how a property from HTMLScriptElement gets sent to this function.

          const shouldExecuteScriptViaMainThread = config.loadScriptsOnMainThread.some(scriptIdentifier => 
            scriptIdentifier === url || scriptIdentifier === id
          )

[teunissenstefan]

Ah understandable. Don’t worry about it. Thanks for letting me know!