Trying to code up a custom lovelace card from Javascript. Where is the documentation?

This is my first look into coding a custom card from the ground up. Been looking at examples on this doc.

I don’t know Polymer that well but I am confused as to where to find the different elements such as the and how to use them, as I would like to pull native elements into my card.

Any resources, documentation, tutorials or guidance would be very helpful.

For example, I would like to pull this entity as is, into my custom card via javascript.

Thank you

That is not an entity, it is a representation of an entity in a user interface.

You could simply use an entity card though to get it represented in lovelace.