solution.js

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);
    }
  }

  const myEmitter = new Emitter(messages);
  const myReceiver = new Receiver();

  myEmitter.setEvent(myReceiver.ping.bind(myReceiver));
  myEmitter.trigger();

  return myReceiver.messages;
};

(() => {
  console.log(solution(['Hello~', 'Can you hear me?', 'Nice to meet you.', 'This is a test message.']));
})();