1 files changed, 11 insertions, 0 deletions
diff --git a/js/globals.ts b/js/globals.ts
index 50f119971..b734b8da3 100644
--- a/js/globals.ts
+++ b/js/globals.ts
@@ -84,6 +84,7 @@ window.setTimeout = timers.setTimeout;
 window.setInterval = timers.setInterval;
 window.location = (undefined as unknown) as domTypes.Location;
 window.onload = undefined as undefined | Function;
+window.onunload = undefined as undefined | Function;
 // The following Crypto interface implementation is not up to par with the
 // standard https://www.w3.org/TR/WebCryptoAPI/#crypto-interface as it does not
 // yet incorporate the SubtleCrypto interface as its "subtle" property.
@@ -171,6 +172,16 @@ window.addEventListener(
     }
   }
 );
+// Registers the handler for window.onunload function.
+window.addEventListener(
+  "unload",
+  (e: domTypes.Event): void => {
+    const onunload = window.onunload;
+    if (typeof onunload === "function") {
+      onunload(e);
+    }
+  }
+);
 
 // below are interfaces that are available in TypeScript but
 // have different signatures