ts-express-sse

A Strongly typed server sent events express middleware for quick & easy node express sse implementation.

This module is strongly typed you'll get useful helpers while coding! You can use both in javascript and typescript projects.

About

ts-express-sse is designed for simplicity. Need to send server-sent events without unnecessary complexity or fallback mechanisms? This library makes it easy.

Installation:

npm install --save ts-express-sse

or

yarn add ts-express-sse

Usage example:

Options:

You can pass an optional options object to the constructor. Currently it only supports changing the way initial data is treated. If you set isSerialized to false, the initial data is sent as a single event. The default value is true.

const sse = new SSE(["Hello world", "Node express sse", "ts-express-sse"], { isSerialized: false, initialEvent: 'optional initial event name' });

Example 1 - Server:

const SSE = require('ts-express-sse');
const express = require('express');
const http  = require ("http") 

// express app
const app = express();
// create sse instance
const sse = new SSE(["Hello world", "Node express sse", "ts-express-sse"]);

app.get('/stream', sse.init);

const content = "sse node js test";

const eventName = "my event";

const customID = Math.random()

// send content 
sse.send(content);
// send content with custom event name
sse.send(content, eventName);
// send content with custom event & custom ID
sse.send(content, eventName, customID);
// Update the data initially served by the SSE stream
sse.updateInit(["array", "containing", "new", "content"]);
// Data to be serialized as a series of events
sse.serialize(["data", "to", "be", "sent", "as", "serialized", "events"]);

// get port
const PORT = process.env.PORT || 8081

// create server
const server =  http.createServer(app);
// Start Server on port 8081
server.listen(PORT, function () {
  console.log(`App started: http://localhost:${PORT}`, );
});

Example 2 - Server ES support:

import SSE from 'ts-express-sse';
import express from 'express'
import http from "http"

// express app
const app = express();
// create an sse instance
const sse = new SSE(["Hello world", "Node express sse", "ts-express-sse"]);

app.get('/stream', sse.init);

const content = "sse node js test";

// send content 
sse.send(content);

// get port
const PORT = process.env.PORT || 8081

// create server
const server =  http.createServer(app);
// Start Server on port 8081
server.listen(PORT, function () {
  console.log(`App started: http://localhost:${PORT}`, );
});

Example 3 - Server - Ping Clients to keep sse active:

import SSE from 'ts-express-sse';
import express from 'express';

// express app
const app = express();

const sse = new SSE(["Node express sse", "ts-express-sse"]);

app.get('/stream', sse.init);

// constantly send sse stream to keep connected clients active to avoid disconnection due to inactivity
setInterval(() => {
  sse.send("Hello, server is active", 'ping');
}, 25000);

// get port
const PORT = process.env.PORT || 8081

// create server
const server =  http.createServer(app);
// Start Server on port 8081
server.listen(PORT, function () {
  console.log(`App started: http://localhost:${PORT}`, );
});

Example 4 - Server - use with compression:

Incase ts-express-sse doesn't work as expected when using it with compression most especially with the latest express version, please use the workaround below;

import SSE from 'ts-express-sse';
import express from 'express'
import http from "http"
import compression from
// express app
const app = express();

// add this workaround
app.use(compression({
  filter: (req, res) =>{
    const outgoingHeaders = res?.getHeaders()
    const contentType = outgoingHeaders['content-type']
    return !contentType?.toString().includes("text/event-stream")
  }
}));
// create an sse instance
const sse = new SSE(["Hello world", "Node express sse", "ts-express-sse"]);

app.get('/stream', sse.init);

const content = "sse node js test";

// send content 
sse.send(content);

// get port
const PORT = process.env.PORT || 8081

// create server
const server =  http.createServer(app);
// Start Server on port 8081
server.listen(PORT, function () {
  console.log(`App started: http://localhost:${PORT}`, );
});

Client - HTML project or React or Nextjs:

const es = new EventSource('http://localhost:8081/stream', );

// // or
// const es = new EventSource('http://localhost:8081/stream', {withCredentials: true} );

es.onmessage = function (event) {
  console.log(event.data)
};

es.addEventListener(eventName, function (event) {
  console.log(event.data)
});

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