From 1e6cef6092995ec871ddb5a7ac05868d95d5d1af Mon Sep 17 00:00:00 2001
From: "byte[]" <byteslice@airmail.cc>
Date: Tue, 11 Aug 2020 01:43:19 -0400
Subject: [PATCH] require confirmation for navigation away from image upload
 form (derpibooru/philomena#164)

---
 assets/js/upload.js | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/assets/js/upload.js b/assets/js/upload.js
index 2be9b9bc..beab2c42 100644
--- a/assets/js/upload.js
+++ b/assets/js/upload.js
@@ -124,6 +124,26 @@ function setupImageUpload() {
   else {
     disableFetch();
   }
+
+  // Catch unintentional navigation away from the page
+
+  function beforeUnload(event) {
+    // Chrome requires returnValue to be set
+    event.preventDefault();
+    event.returnValue = '';
+  }
+
+  function registerBeforeUnload() {
+    window.addEventListener('beforeunload', beforeUnload);
+  }
+
+  function unregisterBeforeUnload() {
+    window.removeEventListener('beforeunload', beforeUnload);
+  }
+
+  fileField.addEventListener('change', registerBeforeUnload);
+  fetchButton.addEventListener('click', registerBeforeUnload);
+  form.addEventListener('submit', unregisterBeforeUnload);
 }
 
 export { setupImageUpload };