How to display sharepoint list items with Javascript

I managed to connect my website with sharepoint with the following code:

var siteUrl = 'mywebsite';
var targetListItem;

SP.SOD.executeFunc('sp.js', 'SP.ClientContext');

var clientContext = new SP.ClientContext(siteUrl);
var oList = clientContext.get_web().get_lists().getByTitle('State_Test');

Once connected I’d like to achieve two goals:

  1. Load all data for each category and use it as a filter (like in a dropdown button);
  2. Display the list items, if possible, by calling it on a text command, not uploading the entire table directly from javascript.

Could anyone give me a direction or any ideas on how I can achieve it? Any suggestions are very welcome!