There is no such thing as an int
in Javascript. All Numbers
are actually doubles behind the scenes* so you can't rely on the type system to issue a rounding order for you as you can in C or C#.
You don't need to worry about precision issues (since doubles correctly represent any integer up to 2^53) but you really are stuck with using Math.floor (or other equivalent tricks) if you want to round to the nearest integer.
*Most JS engines use native ints when they can but all in all JS numbers must still have double semantics.