From a752f019d2472b52100e1cbe71a469d9526e3607 Mon Sep 17 00:00:00 2001
From: honlyHuang <3080820+honlyHuang@users.noreply.github.com>
Date: Mon, 22 Dec 2025 17:59:49 +0800
Subject: [PATCH] fix: child return false in iframe srcdoc

child instanceof HTMLElement has some common pitfalls: google output this:
1. Multiple Realms (iframes): If you check an element created inside an iframe against the HTMLElement constructor of the main window, it will return false. This is because each window/iframe has its own global environment and constructor.
2. SVG Elements: An SVG element is an instance of SVGElement, not HTMLElement. To check for any visible DOM element (including SVG or MathML), you should use child instanceof Element instead.
3. Alternative Property: If you only need to distinguish between nodes and elements without using instanceof, you can check if child.nodeType === 1.
---
 src/embed-webfonts.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/embed-webfonts.ts b/src/embed-webfonts.ts
index a84a699d..1883d9f7 100644
--- a/src/embed-webfonts.ts
+++ b/src/embed-webfonts.ts
@@ -216,8 +216,9 @@ function getUsedFonts(node: HTMLElement) {
     })
 
     Array.from(node.children).forEach((child) => {
-      if (child instanceof HTMLElement) {
-        traverse(child)
+      if (Object.prototype.toString.call(child).includes('HTML') &&
+        child.nodeType === 1) {
+        traverse(child as HTMLElement)
       }
     })
   }