From 81507b9e750228de6d52cb3f7cbd631ecfac3713 Mon Sep 17 00:00:00 2001
From: LASER-Yi <ly0007@yeah.net>
Date: Tue, 24 Aug 2021 09:31:47 +0800
Subject: [PATCH] Add a dialog before closing the page to inform user when
 there're still background tasks running

---
 frontend/src/@modules/task/index.ts | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/frontend/src/@modules/task/index.ts b/frontend/src/@modules/task/index.ts
index aee555b0d..02483e990 100644
--- a/frontend/src/@modules/task/index.ts
+++ b/frontend/src/@modules/task/index.ts
@@ -12,6 +12,17 @@ class BackgroundTask {
   private groups: Task.Group;
   constructor() {
     this.groups = {};
+    window.addEventListener("beforeunload", this.onBeforeUnload.bind(this));
+  }
+
+  private onBeforeUnload(e: BeforeUnloadEvent) {
+    const message = "Background tasks are still running";
+    if (Object.keys(this.groups).length !== 0) {
+      e.preventDefault();
+      e.returnValue = message;
+      return;
+    }
+    delete e["returnValue"];
   }
 
   dispatch<T extends Task.Callable>(groupName: string, tasks: Task.Task<T>[]) {