Yes True, JavaScript doesn't have to do anything with threading, but that is how it still being described in programming world of definition.

"JavaScript is a prototype-based, multi-paradigm, single-threaded, dynamic language, supporting object-oriented, imperative, and declarative (e.g. functional programming) styles."

From MDN so, I would still say its nature is "Single Threaded" , not sure but this will be always a topic of debate.