Can you inject JS in an HML+CSS+Deluge Page?

Can you inject JS in an HML+CSS+Deluge Page?

I have an HTML + CSS + Deluge page and need just a little vanilla JS functionality. 

However, it seems like Zoho Creator does not allow that. I'm required to create a JS widget. 

Is this correct? If so:
1. Won't this quickly consume my API limit if there are a lot of CRUD activities?
2. Am I able to bring in any JS library like htmx or sweetalert2?

What are some best practices or gotchas for JS widgets? Having trouble finding anything other than simple examples on the web.

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