If their point was can you mitigate vendor lock-in, they should have said that instead of asking about self-hosting. Saying you have vendor lock-in because you can't self-host something is very strange in the context of this article.

I didn't make a point of vendor lock-in because migrating this process flow to a self-hosted HTTP server would take about 5 minutes. On top of that, this flow is going to be very similar for any vendor offering javascript functions.

Perhaps it is my fault for not including a section discussing this, but I assumed that the audience for this would primarily be people understand basic javascript and could deduce the portability of the code by looking at it.