From d37a44536952be88baaf092d044348ddfc2f1227 Mon Sep 17 00:00:00 2001
From: Jonathan Grimes <jsg2021@users.noreply.github.com>
Date: Thu, 17 Sep 2020 12:47:55 -0500
Subject: [PATCH] Refactor the container/viewer checks in the BaseViewer
 constructor The previous checks prevented specifying a container/viewer that
 was in another document/window. Fixes #12385

---
 web/base_viewer.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/web/base_viewer.js b/web/base_viewer.js
index 36c63cba0..a151a8673 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -150,8 +150,10 @@ class BaseViewer {
     ) {
       if (
         !(
-          this.container instanceof HTMLDivElement &&
-          this.viewer instanceof HTMLDivElement
+          this.container &&
+          this.container.tagName.toUpperCase() === "DIV" &&
+          this.viewer &&
+          this.viewer.tagName.toUpperCase() === "DIV"
         )
       ) {
         throw new Error("Invalid `container` and/or `viewer` option.");