fix: silently close the transport in the beforeunload hook

Related:

- socketio/socket.io#3639
- socketio/socket.io#3069

lib/socket.js

@@ -90,6 +90,20 @@ class Socket extends Emitter {
     // set on heartbeat
     this.pingTimeoutTimer = null;
 
+    if (typeof addEventListener === "function") {
+      addEventListener(
+        "beforeunload",
+        () => {
+          if (this.transport) {
+            // silently close the transport
+            this.transport.removeAllListeners();
+            this.transport.close();
+          }
+        },
+        false
+      );
+    }
+
     this.open();
   }
 

lib/transports/polling-jsonp.js

@@ -10,12 +10,6 @@ const rEscapedNewline = /\\n/g;
 
 let callbacks;
 
-/**
- * Noop.
- */
-
-function empty() {}
-
 class JSONPPolling extends Polling {
   /**
    * JSONP Polling constructor.
@@ -46,17 +40,6 @@ class JSONPPolling extends Polling {
 
     // append to query string
     this.query.j = this.index;
-
-    // prevent spurious errors from being emitted when the window is unloaded
-    if (typeof addEventListener === "function") {
-      addEventListener(
-        "beforeunload",
-        function() {
-          if (self.script) self.script.onerror = empty;
-        },
-        false
-      );
-    }
   }
 
   /**
@@ -73,6 +56,8 @@ class JSONPPolling extends Polling {
    */
   doClose() {
     if (this.script) {
+      // prevent spurious errors from being emitted when the window is unloaded
+      this.script.onerror = () => {};
       this.script.parentNode.removeChild(this.script);
       this.script = null;
     }

lib/transports/websocket.js

@@ -201,6 +201,7 @@ class WS extends Transport {
   doClose() {
     if (typeof this.ws !== "undefined") {
       this.ws.close();
+      this.ws = null;
     }
   }