Event emitter with closure

class Event {
  constructor() {
    this.cb = () => {};
  }

  on(newEvent, cb) {
    const oldCb = this.cb;

    this.cb = event => {
      oldCb(event);
      if (newEvent === event) {
        cb();
      }
    };
  }

  emit(event) {
    this.cb(event);
  }
}

const EE = new Event();

EE.on("login", () => console.log("Hi1"));
EE.on("login", () => console.log("Hi2"));
EE.on("login", () => console.log("Hi3"));
EE.on("logout", () => console.log("Bye1"));
EE.on("logout", () => console.log("Bye2"));
EE.on("logout", () => console.log("Bye3"));

EE.emit("login");
EE.emit("logout");