Need to get rid of Trojan(s) etc.

Put in a top notch spam filter and do not receive emails with viruses. I get none.
Make sure any USB keys you have or are given do not have viruses.
Scan with your own Anti Virus followed by a scan with Malwarebytes.

In "the old days" we used to be able to manually remove viruses and other nasty stuff from computers.

Nowadays, it is too difficult as the software is really good at hiding. Best approach is to scan your system with an up to date antivirus program and let it clean up for you.

*However*, I would recommend wiping your system, reinstall Windows and restore your data from backup. This is the best way to ensure your system is clean. Following that, take steps such as what John mentioned to prevent future infections.

You should be looking at this multiple ways: certainly the removal is important, and has been addressed. But just as important is preventing future infections. Aside from the previously mentioned, a web proxy would be a great way to prevent infected files from the web. As well as a service like Umbrella, where bad sites are getting blocked at the level of DNS lookups.

First, do away with SEP. Secondly that is a heuristic detection of a dropper. A dropper does not contain the actual payload so do not just wipe your computer because you get a warning.
Your computer might not even be infected, just a target of something trying to infect it.

Seeing that it is a JS file seems that something is downloading it via web.

Do you ask about removing it from one computer or from a computer network?
I assume you have some AV installed, can you post at least one alert related to this infection?

I would also suggest to scan affected computer with different types of AV (Bitdefender, Kaspersky, etc.)

for author advice