Classes emitter and receiver are supposed to send and receive messages. Why is the receiver not receiving any messages and how should I fix it?

const solution = (messages) => {
    class Emitter {
        constructor(messages = []) {
            this.messages = messages;
            this.event = () => {};
        }
        setEvent(fn) {
            this.event = fn;
        }
        trigger() {
            this.messages.forEach(message => this.event(message));
        }
    }
    
    class Receiver {
        constructor() {
            this.messages = [];
        }
        ping(message) {
            this.messages.push(message);
        }
    }
    
    let emi = new Emitter(messages);
    let rec = new Receiver();
    emi.setEvent(rec.ping);
    emi.trigger();
    console.log(rec.messages); // []
    console.log(emi.messages) // ['hi','hola','hi','hola']
}
solution(['hi','hola']);