Dispatch a server sent event to the client. The event type will be sent as event: to the client which will be raised as a MessageEvent on the EventSource in the client.

Any local event handlers will be dispatched to first, and if the event is cancelled, it will not be sent to the client.

import { Application, ServerSentEvent } from "https://deno.land/x/oak/mod.ts";

const app = new Application();

app.use((ctx) => {
   const sse = ctx.getSSETarget();
   const evt = new ServerSentEvent("ping", "hello");
   sse.dispatchEvent(evt);
});

await app.listen();