JavaScript

So strip out the typescript.
Or compile it, and use the result. Typescript doesn't minify, so worst case is you have some odd looking code. But it will be functionally the same.
If you are really lazy, feed it into chatgpt and ask it to remove the typescript.

That is the Web UI frontend. It's designed to run in the browser.
That is the literal reference implementation. That is what the Lemmy Devs coded as the web fronted to work with the Lemmy backend, as deployed on all (maybe, most) Lemmy instances.
It's not any 3rd party reimplementation. It's not example code.
It is the 1st party, guaranteed to be correct, Lemmy markdown processor.
You won't find a better reference.

Figure it out yourself then.