As you will have read, the void operator evaluates its operand and then results in the value undefined. When you call setTimeout, it returns a number (the timer handle). So void setTimeout(...) results in undefined instead of a number.
If the code is really as you've shown it, there's no purpose whatsoever to the void operator there, because the return value from setTimeout isn't being used for anything.
[I've removed the bit I wrote about CoffeeScript, as I couldn't create an example; the CoffeeScript compiler complained that void is a reserved word (which it is, but that's why I was using it). I don't do CoffeeScript, so figured best to just remove that.]
