Use your computer as a server for js [closed]

I have a website and I simply want a way to creat an account and sign in, with username and password in js, that’s the easy part, I don’t know how to host a server, is there a free way? I simply need somewhere to store the username and password pair, it does not have to be encrypted or anything but it would be a nice bonus. Is there a way to do this for free? The amount of data won’t really be that much. And what language would up I use to get data from it, could I use js? Any help would be greatly appreciated:)