Node ssr module ReferenceError:

I am new to Node so I'm not sure what is happening with my SSR code.
One of the imported modules uses MutationObserver which I though I could handle by defining a shim for this class inside another module which I import before the problematic module.

Something like this should work I thought:

import './app/server-rendering';
import {render} from '../packages/lit-labs-ssr'; // <-- module that uses MutationObserver


server-rendering.ts:

// @ts-ignore: Override the global MutationObserver in SSR
class MutationObserver {
observe() {
// No-op in SSR
}

disconnect() {
// No-op in SSR
}

takeRecords() {
// No-op in SSR
return [];
}
}

// @ts-ignore: Override the global MutationObserver in SSR
global.MutationObserver = MutationObserver;


Could someone please explain why this doesn't work.

Error:

12:27:53 AM [vite] Error when evaluating SSR module /@fs/C:/Users/illus/VSProjects/SluzbeniList/AngularApp/.angular/cache/19.0.7/AngularApp/vite/deps_ssr/chunk-QVHPIT5W.js?v=a381c8e8:
|- ReferenceError: MutationObserver is not defined
at eval (C:\Users\illus\VSProjects\SluzbeniList\AngularApp\.angular\cache\19.0.7\AngularApp\vite\deps_ssr\chunk-QVHPIT5W.js:27:19)
at async instantiateModule (file:///C:/Users/illus/VSProjects/SluzbeniList/AngularApp/node_modules/vite/dist/node/chunks/dep-CB_7IfJ-.js:52972:5)

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