The short answer: No.
Execution time of Javascript code is highly dependent on a number of factors, the largest and most varied is the garbage collector. It's fairly easy to come up with code which, when ran and timed a large number of times, is orders of magnitude slower some of those times, depending on how much work the garbage collector decides to do during allocations during the run. And, in Javascript, nearly *everything* creates allocations and garbage.
The most reliable sandboxing would probably be to start an entirely separate process, but even that, I suspect, will be pretty highly variable in terms of performance (and, of course, have huge amounts of overhead if the Javascript you're running is relatively small).