Is it possible to program Arduino in transpiled JavaScript?
Even if such a transpiler exists (which I don‘t know) you will still have to deal with the loop structure and the fact that you should avoid using delays. On a microcontroller you have to forget about things like multithreading and even dynamic memory allocation should be used carefully.
Most of those things that make a programmer‘s life easy on bigger systems are usually paid with ram or cpu power, but on a microcontroller with some kB RAM there are only few resources to pay with.

So my recommendation is to learn C++ instead of looking for ways to convert code from another language, which will probably introduce its own problems. You‘ll soon find yourself one layer below and there are exciting things that higher languages hide from you.