Component.svelte

<script>
import {publish, subscribe} from './pubsub'
import {onMessageEvent} from './project-events'
import {onMount} from 'svelte'

let message;

//Listen the event onMount and unscubscribe when return.
onMount(()=>{
 let onMsg = subscribe(onMessageEvent, (msg)=>{
   console.log('Received:', msg); });
 return()=>{ onMsg.unsubscribe(); }
});

//Send message using publish event
const onSend = ()=>{
  publish(new onMessageEvent({message}));
};
</script>

<input bind:value={message}/>
<button on:click={onSend}>Send</button>