function commitBeforeMutationEffects_begin() {
  while (nextEffect !== null) {
    var fiber = nextEffect; // TODO: Should wrap this in flags check, too, as optimization

    var deletions = fiber.deletions;

    if (deletions !== null) {
      for (var i = 0; i < deletions.length; i++) {
        var deletion = deletions[i];
        commitBeforeMutationEffectsDeletion(deletion);
      }
    }

    var child = fiber.child;

    if ((fiber.subtreeFlags & BeforeMutationMask) !== NoFlags && child !== null) {
      ensureCorrectReturnPointer(child, fiber);
      nextEffect = child;
    } else {
      commitBeforeMutationEffects_complete();
    }
  }
}

function commitBeforeMutationEffects_complete() {
  while (nextEffect !== null) {
    var fiber = nextEffect;

    {
      setCurrentFiber(fiber);
      invokeGuardedCallback(null, commitBeforeMutationEffectsOnFiber, null, fiber);

      if (hasCaughtError()) {
        var error = clearCaughtError();
        captureCommitPhaseError(fiber, fiber.return, error);
      }

      resetCurrentFiber();
    }

    var sibling = fiber.sibling;

    if (sibling !== null) {
      ensureCorrectReturnPointer(sibling, fiber.return);
      nextEffect = sibling;
      return;
    }

    nextEffect = fiber.return;
  }
}