From c361bc691f510b96f8909c5e6c62a4635d50275c Mon Sep 17 00:00:00 2001
From: Damien Arrachequesne <damien.arrachequesne@gmail.com>
Date: Tue, 2 Mar 2021 09:02:42 +0100
Subject: [PATCH] feat: listen to the "offline" event

The connection will be closed once the "offline" event is emitted by
the browser, in order not to wait for the heartbeat mechanism to detect
the disconnection.

Reference: https://developer.mozilla.org/en-US/docs/Web/API/Window/offline_event

Related: https://github.com/socketio/socket.io-client/issues/1433
---
 lib/socket.js | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/socket.js b/lib/socket.js
index e8781d37b..ec283d393 100644
--- a/lib/socket.js
+++ b/lib/socket.js
@@ -102,6 +102,12 @@ class Socket extends Emitter {
         },
         false
       );
+      if (this.hostname !== "localhost") {
+        this.offlineEventListener = () => {
+          this.onClose("transport close");
+        };
+        addEventListener("offline", this.offlineEventListener, false);
+      }
     }
 
     this.open();
@@ -622,6 +628,10 @@ class Socket extends Emitter {
       // ignore further transport communication
       this.transport.removeAllListeners();
 
+      if (typeof removeEventListener === "function") {
+        removeEventListener("offline", this.offlineEventListener, false);
+      }
+
       // set ready state
       this.readyState = "closed";