This is a simple SSE-server in node.js. The server can handle subscribers to multiple topics/categories.

To use the server in your code:

// include the file:
const sse = require('./sse');

// example, sending events to topic "topic1" every second:
setInterval(() => {
  sse.internalSendEvent({message: 'Hello from topic1!'}, 'topic1');
}, 1000);

Sending events require two params:

• data (JSON object)
• topic (string). This creates a subscribable endpoint to the client (/events/:topic)

You can also create an endpoint for posting events from an external source:

app.post('/sendevent/:topic', sse.externalSendEvent);

var sse = new EventSource('/events/topic1');
sse.onmessage = function(e) {
    console.log(JSON.parse(e.data));
};

I made this just for fun. To use it in production enviroment you should refactor the code, add CORS-policys, logging, error handeling etc.