I was just about to ask the same question. I believe the job system does not work on WebGL, and I am wondering if it is even worth using the ECS without the job system. They seem to be pretty closely integrated and the syntax is entirely different if you are not using it. I would like feedback on this also because I’m trying to decide if I should wait until multithreading comes to WebGL before I start using ECS.
Edit: It looks like jobs will work in 2019.1 , at least experimentally.