fix(runtime): fix recursive dispatches of unload event (#9207)

2 files changed, 15 insertions, 3 deletions

diff --git a/runtime/js/30_os.js b/runtime/js/30_os.js
index 1d700b561..5a3c990b0 100644
--- a/runtime/js/30_os.js
+++ b/runtime/js/30_os.js
@@ -24,9 +24,12 @@
   }
 
   function exit(code = 0) {
-    // Invokes the `unload` hooks before exiting
-    // ref: https://github.com/denoland/deno/issues/3603
-    window.dispatchEvent(new Event("unload"));
+    // Dispatches `unload` only when it's not dispatched yet.
+    if (!window[Symbol.for("isUnloadDispatched")]) {
+      // Invokes the `unload` hooks before exiting
+      // ref: https://github.com/denoland/deno/issues/3603
+      window.dispatchEvent(new Event("unload"));
+    }
     core.jsonOpSync("op_exit", { code });
     throw new Error("Code not reachable");
   }
diff --git a/runtime/js/99_main.js b/runtime/js/99_main.js
index a6abc8d27..fd846af20 100644
--- a/runtime/js/99_main.js
+++ b/runtime/js/99_main.js
@@ -305,6 +305,15 @@ delete Object.prototype.__proto__;
     defineEventHandler(window, "load", null);
     defineEventHandler(window, "unload", null);
 
+    const isUnloadDispatched = Symbol.for("isUnloadDispatched");
+    // Stores the flag for checking whether unload is dispatched or not.
+    // This prevents the recursive dispatches of unload events.
+    // See https://github.com/denoland/deno/issues/9201.
+    window[isUnloadDispatched] = false;
+    window.addEventListener("unload", () => {
+      window[isUnloadDispatched] = true;
+    });
+
     runtimeStart(runtimeOptions);
     const {
       args,