Function handler

packages/engine.io-client/test/connection.js:231–237

()

      socket.on("open", () => {
        const handler = () => {
          expect(socket.transport.readyState).to.eql("closed");
          expect(() => socket.write("ignored")).to.not.throwException();

          removeEventListener("beforeunload", handler, false);
          done();
        };

        addEventListener("beforeunload", handler, false);
        dispatchEvent(createEvent("beforeunload"));