Function reconcileChildrenIterator

docs/index.js:6677–6752

(
    returnFiber,
    currentFirstChild,
    newChildren,
    lanes
  )

    return resultingFirstChild;
  }
  function reconcileChildrenIterator(
    returnFiber,
    currentFirstChild,
    newChildren,
    lanes
  ) {
    if (null == newChildren) throw Error(formatProdErrorMessage(151));
    for (
      var resultingFirstChild = null,
        previousNewFiber = null,
        oldFiber = currentFirstChild,
        newIdx = (currentFirstChild = 0),
        nextOldFiber = null,
        step = newChildren.next();
      null !== oldFiber && !step.done;
      newIdx++, step = newChildren.next()
    ) {
      oldFiber.index > newIdx
        ? ((nextOldFiber = oldFiber), (oldFiber = null))
        : (nextOldFiber = oldFiber.sibling);
      var newFiber = updateSlot(returnFiber, oldFiber, step.value, lanes);
      if (null === newFiber) {
        null === oldFiber && (oldFiber = nextOldFiber);
        break;
      }
      shouldTrackSideEffects &&
        oldFiber &&
        null === newFiber.alternate &&
        deleteChild(returnFiber, oldFiber);
      currentFirstChild = placeChild(newFiber, currentFirstChild, newIdx);
      null === previousNewFiber
        ? (resultingFirstChild = newFiber)
        : (previousNewFiber.sibling = newFiber);
      previousNewFiber = newFiber;
      oldFiber = nextOldFiber;
    }
    if (step.done)
      return (
        deleteRemainingChildren(returnFiber, oldFiber),
        isHydrating && pushTreeFork(returnFiber, newIdx),
        resultingFirstChild
      );
    if (null === oldFiber) {
      for (; !step.done; newIdx++, step = newChildren.next())
        (step = createChild(returnFiber, step.value, lanes)),
          null !== step &&
            ((currentFirstChild = placeChild(step, currentFirstChild, newIdx)),
            null === previousNewFiber
              ? (resultingFirstChild = step)
              : (previousNewFiber.sibling = step),
            (previousNewFiber = step));
      isHydrating && pushTreeFork(returnFiber, newIdx);
      return resultingFirstChild;
    }
    for (
      oldFiber = mapRemainingChildren(oldFiber);
      !step.done;
      newIdx++, step = newChildren.next()