Is it possible to have JS and NOT know you have it?
Non-technical answer: Yes.
So how the hell do you mitigate this ? Text based browsers that don't support JS are one option. (Welcome to the 1990's)
A JS blocker like the NoScript suite
(firefox) or ScriptNo
(Chrome / Chromium) will handle most of these threats. ScriptNo has been renamed to ScriptSafe
...on Chrome Webstore.
The thing is, JS and JS libraries are ubiquitous on the web. Some pages won't even load because they are written entirely in JS with no fallback (stupid business practices / model) to a non-JS page. Luckily, there aren't many pages like that, yet.
If you want fine grained control, try uBlock Origin
- (WebSocket not required in FFx) It can be confusing at first because you are presented with tons of information, so read the documentation.
These are self learning addons, but they take a bit of getting used to at first. Blocking JS is the most important
thing you can do to protect yourself online (for the average user.)