Function applyForeignNodes

packages/core/src/render3/node_manipulation.ts:911–952

(
  renderer: Renderer,
  action: WalkTNodeTreeAction,
  lView: LView,
  parent: RElement | null,
  beforeNode: RNode | null,
)

}

function applyForeignNodes(
  renderer: Renderer,
  action: WalkTNodeTreeAction,
  lView: LView,
  parent: RElement | null,
  beforeNode: RNode | null,
) {
  const tView = lView[TVIEW];
  const headTNode = tView.firstChild!;
  const tailTNode = headTNode.next!;
  const head = unwrapRNode(lView[headTNode.index]);
  const tail = unwrapRNode(lView[tailTNode.index]);

  const fragmentSlotIndex = tailTNode.index + 1;
  let fragment = lView[fragmentSlotIndex] as any;

  if (action === WalkTNodeTreeAction.Insert || action === WalkTNodeTreeAction.Create) {
    if (parent !== null) {
      if (fragment && fragment.hasChildNodes()) {
        nativeInsertBefore(renderer, parent, fragment, beforeNode, true);
      } else {
        nativeInsertBefore(renderer, parent, head!, beforeNode, true);
        nativeInsertBefore(renderer, parent, tail!, beforeNode, true);
      }
    }
  } else if (action === WalkTNodeTreeAction.Detach) {
    if (!fragment) {
      fragment = document.createDocumentFragment();
      lView[fragmentSlotIndex] = fragment;
    }
    if (head && head.parentNode === fragment) {
      return;
    }
    let current: RNode | null = head;
    while (current !== null) {
      const next: RNode | null = current.nextSibling;
      fragment.appendChild(current);
      if (current === tail) break;
      current = next;
    }
  }
}

/**
 * `applyProjection` performs operation on the projection.