How to implement the stroke functionality?

Question

JavaScript

I'm trying to make an implementation of stroke like on the piskel
site My project is simple-piskel.surge.sh/app/index.html

How to make exactly this kind of line drawing implementation?
Can you tell me some material on the topic or give a couple of tips on how best to do this, since my implementation is bad ...

Answer 1

It turned out clumsy, well, the first thing that came to mind.
https://jsfiddle.net/twobomb/uyf27q0k/