expressjsHow can I use Server-Sent Events (SSE) with Express.js?

Server-Sent Events (SSE) is a web technology that allows a web server to push data to a client (browser). It can be used with Express.js to create real-time applications.

To use SSE with Express.js, you need to install the express-sse package.

npm install express-sse

Then you need to create a new Express.js application and add the express-sse package to it.

const express = require('express');
const sse = require('express-sse');

const app = express();

// Create an instance of the SSE middleware
const sseMiddleware = new sse();

// Add the middleware to the Express.js app
app.use(sseMiddleware);

You can then use the sseMiddleware.send() method to send data to the client.

// Send data to the client
sseMiddleware.send({
  message: 'Hello from the server!'
});

The client can then listen for the data using the EventSource API.

// Create an EventSource
const eventSource = new EventSource('/sse');

// Listen for data
eventSource.onmessage = (event) => {
  console.log(event.data); // Outputs 'Hello from the server!'
};

Helpful links

• Express.js
• express-sse
• Server-Sent Events

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