fix: allow integers as event names

This commit restores the possibility to use integers as event names,
which was possible in Socket.IO v2.

Author: darrachequesne

lib/index.ts

@@ -245,7 +245,7 @@ export class Decoder extends Emitter {
         return typeof payload === "string" || typeof payload === "object";
       case PacketType.EVENT:
       case PacketType.BINARY_EVENT:
-        return Array.isArray(payload) && typeof payload[0] === "string";
+        return Array.isArray(payload) && payload.length > 0;
       case PacketType.ACK:
       case PacketType.BINARY_ACK:
         return Array.isArray(payload);

test/parser.js

@@ -47,6 +47,17 @@ describe("parser", () => {
     );
   });
 
+  it("encodes an event (with an integer as event name)", (done) => {
+    helpers.test(
+      {
+        type: PacketType.EVENT,
+        data: [1, "a", {}],
+        nsp: "/",
+      },
+      done
+    );
+  });
+
   it("encodes an event (with ack)", (done) => {
     helpers.test(
       {