8 files changed, 94 insertions, 7 deletions
diff --git a/cli/lsp/testing/execution.rs b/cli/lsp/testing/execution.rs
index 6b4e947a0..83f74e5ed 100644
--- a/cli/lsp/testing/execution.rs
+++ b/cli/lsp/testing/execution.rs
@@ -226,6 +226,12 @@ async fn test_specifier(
 
     worker.js_runtime.resolve_value(test_result).await?;
 
+    loop {
+      if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+        break;
+      }
+      worker.run_event_loop(false).await?;
+    }
     worker.dispatch_unload_event(&located_script_name!())?;
   }
 
diff --git a/cli/main.rs b/cli/main.rs
index e74ed8518..de44add17 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -639,7 +639,13 @@ async fn eval_command(
   }
   worker.execute_main_module(&main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(false).await?;
+  loop {
+    worker.run_event_loop(false).await?;
+
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
   Ok(0)
 }
@@ -975,7 +981,12 @@ async fn run_from_stdin(flags: Flags) -> Result<i32, AnyError> {
   }
   worker.execute_main_module(&main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(false).await?;
+  loop {
+    worker.run_event_loop(false).await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
   Ok(worker.get_exit_code())
 }
@@ -1014,7 +1025,15 @@ async fn run_with_watch(flags: Flags, script: String) -> Result<i32, AnyError> {
       self.worker.dispatch_load_event(&located_script_name!())?;
       self.pending_unload = true;
 
-      let result = self.worker.run_event_loop(false).await;
+      let result = loop {
+        let result = self.worker.run_event_loop(false).await;
+        if !self
+          .worker
+          .dispatch_beforeunload_event(&located_script_name!())?
+        {
+          break result;
+        }
+      };
       self.pending_unload = false;
 
       if let Err(err) = result {
@@ -1162,9 +1181,16 @@ async fn run_command(
   }
 
   worker.dispatch_load_event(&located_script_name!())?;
-  worker
-    .run_event_loop(maybe_coverage_collector.is_none())
-    .await?;
+
+  loop {
+    worker
+      .run_event_loop(maybe_coverage_collector.is_none())
+      .await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
 
   if let Some(coverage_collector) = maybe_coverage_collector.as_mut() {
diff --git a/cli/standalone.rs b/cli/standalone.rs
index d66eb7694..50baf70ea 100644
--- a/cli/standalone.rs
+++ b/cli/standalone.rs
@@ -316,7 +316,14 @@ pub async fn run(
   );
   worker.execute_main_module(main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(true).await?;
+
+  loop {
+    worker.run_event_loop(false).await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
   std::process::exit(0);
 }
diff --git a/cli/tests/integration/run_tests.rs b/cli/tests/integration/run_tests.rs
index bd27cd8dd..1cd1db0ef 100644
--- a/cli/tests/integration/run_tests.rs
+++ b/cli/tests/integration/run_tests.rs
@@ -249,6 +249,12 @@ itest!(webstorage_serialization {
   output: "webstorage/serialization.ts.out",
 });
 
+// tests the beforeunload event
+itest!(beforeunload_event {
+  args: "run before_unload.js",
+  output: "before_unload.js.out",
+});
+
 // tests to ensure that when `--location` is set, all code shares the same
 // localStorage cache based on the origin of the location URL.
 #[test]
diff --git a/cli/tests/testdata/before_unload.js b/cli/tests/testdata/before_unload.js
new file mode 100644
index 000000000..2572e512b
--- /dev/null
+++ b/cli/tests/testdata/before_unload.js
@@ -0,0 +1,21 @@
+let count = 0;
+
+console.log("0");
+
+globalThis.addEventListener("beforeunload", (e) => {
+  console.log("GOT EVENT");
+  if (count === 0 || count === 1) {
+    e.preventDefault();
+    setTimeout(() => {
+      console.log("3");
+    }, 100);
+  }
+
+  count++;
+});
+
+console.log("1");
+
+setTimeout(() => {
+  console.log("2");
+}, 100);
diff --git a/cli/tests/testdata/before_unload.js.out b/cli/tests/testdata/before_unload.js.out
new file mode 100644
index 000000000..f1f2ab49a
--- /dev/null
+++ b/cli/tests/testdata/before_unload.js.out
@@ -0,0 +1,8 @@
+0
+1
+2
+GOT EVENT
+3
+GOT EVENT
+3
+GOT EVENT
diff --git a/cli/tools/bench.rs b/cli/tools/bench.rs
index 3c40b4e95..3a40a4e97 100644
--- a/cli/tools/bench.rs
+++ b/cli/tools/bench.rs
@@ -404,6 +404,12 @@ async fn bench_specifier(
 
   worker.js_runtime.resolve_value(bench_result).await?;
 
+  loop {
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+    worker.run_event_loop(false).await?;
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
 
   Ok(())
diff --git a/cli/tools/test.rs b/cli/tools/test.rs
index ac146fdbf..71374d94e 100644
--- a/cli/tools/test.rs
+++ b/cli/tools/test.rs
@@ -814,6 +814,13 @@ async fn test_specifier(
 
   worker.js_runtime.resolve_value(test_result).await?;
 
+  loop {
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+    worker.run_event_loop(false).await?;
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
 
   if let Some(coverage_collector) = maybe_coverage_collector.as_mut() {