app.ts

declare global {
	interface Window {
		Pusher: any
	}
}

import Echo from 'laravel-echo'
window.Pusher = require('pusher-js')

window.Echo = new Echo({
	broadcaster: 'pusher',
	key: 'ad6bcb7780f189a3746e',
	cluster: 'us3',
	forceTLS: true,
})

const channel = window.Echo.channel('toast-channel')

channel.listen('.toast-event', function(data) {
	alert(JSON.stringify(data))
})

ToastMessage.php

<?php

namespace App\Events;

use Illuminate\Broadcasting\Channel;
use Illuminate\Broadcasting\InteractsWithSockets;
use Illuminate\Broadcasting\PresenceChannel;
use Illuminate\Broadcasting\PrivateChannel;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;
use Illuminate\Foundation\Events\Dispatchable;
use Illuminate\Queue\SerializesModels;

class ToastMessage implements ShouldBroadcast
{
    use Dispatchable, InteractsWithSockets, SerializesModels;
    public $message;

    /**
     * Create a new event instance.
     *
     * @return void
     */
    public function __construct($message)
    {
        $this->message = $message;
    }

    /**
     * Get the channels the event should broadcast on.
     *
     * @return \Illuminate\Broadcasting\Channel|array
     */
    public function broadcastOn()
    {
        return new Channel('toast-channel');
        // return new PrivateChannel('toast.' . $this->user);
    }

    public function broadcastAs()
    {
        return 'toast-message';
    }
}