videostore | videostore example from Martin Fowler

First of all, I think you should use the react's state, to handle data changes through selected items like you are trying to do. moreover, in showCat function, there is a problem, let's say you are getting the relevant data you need, but you are not using it or storing it for future use, so at the end of the function the data is not stored and you are losing it. Therefore, you are not holding the selected id that you need for presenting the relevant stores.

1. Add new useState for holding the current selected catID like so:
   const [selectedCatID, setSelectedCatID] = useState();

2. function showCat(catid) { setSelectedCatID(catid); }

Then change the div attribute to pass the item.id through the onClick's function at triggering showCat. 3)

1. Lastly modify the jsx to show the relevant stores by the current selected catid: