The (New) Standard `for` Loop

for (var i = 0, j = foo.length; i < j; i++) {
  // do stuff
}

for (var i = foo.length; i;) {
  // first usage in loop: blah[--i]
  // do stuff slightly faster in reverse order
}

That might be the case in the particular version of Chrome 6 you were using to test. In the tests I performed, however, there was a greater than 1% difference.