sse-emitter

Server-Sent Events as simple as they can get

Bind an instance to a route and emit events named after the matched path.

For example, if you bind to route /hello, when you emit event /hello, browsers listening on this endpoint will get the event data.

If you bind to route /hello/:name, you can send messages to browsers having EventSource('/hello/world') and EventSource('/hello/sse') by emitting respectively /hello/world and /hello/sse events. This makes implementing chatroom-like or channel-like functionnality a breeze. See usage.

Of course a single emitter can be bound to as many routes as you like. Also, the bind method returns a simple handler and doesn't prevent you from adding middleware, eg. for authentication.

Installation

$ npm install sse-emitter

Usage

var express = require('express');
var SSE = require('sse-emitter');
 
var sse = new SSE({
  keepAlive: 30000, // in ms, defaults to 10000
  encoder: JSON.stringify // this is the default anyway, but could be btoa(), ...
});
 
var app = express();
 
app.get('/channel/:id', sse.bind());
 
app.listen(5000);
 
setInterval(function() {
  sse.emit('/channel/1', {
    text: "Hello, SSE !"
  });
}, 1000);
 

Then browser-side :

var channel = new EventSource('/channel/1');
channel.addEventListener('message', function(ev) {
  console.log(JSON.parse(ev.data));
});