Vocabulary

EventStream: What the server sends to the client.
- It's a text stream with a specific format
EventSource: A browser API to consume an EventStream

Consuming SSE in the browser

The browser has a built-in API, EventSource to consume server-sent events.

Point to a URL that serves an event stream via GET request.
Listen to the onmessage event

eventSource.js

const eventSource = new EventSource("/api/my-event-stream");
eventSource.onmessage = (event) => {
  // event.data is always a string. So you may need JSON.parse()
  console.log(event.data);
};