sharepoint online – PowerApps forms when the text is filled do an action

I have a question regarding PowerApp forms in SharePoint Online.

By and large, in the annual versions of SharePoint, when there were only forms, I could use javascript to retrieve a value from a list based on the input of ############################################################################## 39, a particular TaxnomyField.

Now, I'm testing SharePoint online and I wonder how can I get the same thing? If I understood correctly, it is not possible to add javascript, what are my other options?

It is also important to know that this should only be available when you add a new item. It can be automatically or with a push of a button.

cordially