From 5cbe5db35155e3a9790a30de09feb17843053b7a Mon Sep 17 00:00:00 2001
From: earshinov <earshinov@gmail.com>
Date: Sun, 7 Apr 2019 09:44:01 +0300
Subject: [PATCH] fix: prevent unhandled promise rejections for hidden frames
 (#1762)

---
 src/Clone.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Clone.js b/src/Clone.js
index 553e21b..2d8058b 100644
--- a/src/Clone.js
+++ b/src/Clone.js
@@ -213,7 +213,12 @@ export class DocumentCloner {
                         new Promise((resolve, reject) => {
                             const iframeCanvas = document.createElement('img');
                             iframeCanvas.onload = () => resolve(canvas);
-                            iframeCanvas.onerror = reject;
+                            iframeCanvas.onerror = function(event) {
+                                // Empty iframes may result in empty "data:," URLs, which are invalid from the <img>'s point of view
+                                // and instead of `onload` cause `onerror` and unhandled rejection warnings
+                                // https://github.com/niklasvh/html2canvas/issues/1502
+                                iframeCanvas.src == 'data:,' ? resolve(canvas) : reject(event);
+                            };
                             iframeCanvas.src = canvas.toDataURL();
                             if (tempIframe.parentNode) {
                                 tempIframe.parentNode.replaceChild(