# express-longpoll > Lightweight long polling for express.js with TypeScript support Latest version **1.0.3** (published 2025-12-11) · ISC license · 0 weekly downloads ## Install ```sh npm install express-longpoll pnpm add express-longpoll yarn add express-longpoll bun add express-longpoll ``` ## Health **Score 55/100 (C)** — status: stable. Positive: has types; no vulnerabilities; high quality score. Warnings: low downloads; no esm support. ## Facts | | | |---|---| | Version | 1.0.3 | | Published | 2025-12-11 | | First published | 2017-01-29 | | Weekly downloads | 0 | | License | ISC | | TypeScript types | bundled | | Module format | CommonJS | | Node | >=14.0.0 | | Dependencies | 3 | | Unpacked size | 21.9 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 33 | | Author | Yehya Awad | | Maintainers | yehyaawad | | Keywords | express, longpoll, long-polling, realtime, comet, typescript | ## Links - npm: https://www.npmjs.com/package/express-longpoll - Repository: https://github.com/yehya/express-longpoll - Homepage: https://github.com/yehya/express-longpoll#readme - Issues: https://github.com/yehya/express-longpoll/issues - npm.io page: https://npm.io/package/express-longpoll ## Dependencies (3) - [lodash](https://npm.io/package/lodash.md) >=4.17.21 - [bluebird](https://npm.io/package/bluebird.md) ^3.5.0 - [eventemitter2](https://npm.io/package/eventemitter2.md) ^5.0.1 ## Alternatives - [@opentelemetry/exporter-zipkin](https://npm.io/package/@opentelemetry/exporter-zipkin.md) — 14.8M weekly downloads - [pusher-js](https://npm.io/package/pusher-js.md) — 2.0M weekly downloads - [browserify](https://npm.io/package/browserify.md) — 1.7M weekly downloads - [sqs-consumer](https://npm.io/package/sqs-consumer.md) — 1.7M weekly downloads - [@sanity/eventsource](https://npm.io/package/@sanity/eventsource.md) — 930.8K weekly downloads ## Recent versions - 1.0.3 (latest) — 2025-12-11 - 1.0.1 — 2025-12-11 - 1.0.0 — 2025-12-11 - 0.0.6 — 2019-10-19 - 0.0.4 — 2017-08-07 - 0.0.3 — 2017-08-07 - 0.0.2 — 2017-02-08 - 0.0.1 — 2017-01-29 ## README [![Build Status](https://travis-ci.org/yehya/express-longpoll.svg?branch=master)](https://travis-ci.org/yehya/express-longpoll) [![npm version](https://badge.fury.io/js/express-longpoll.svg)](https://badge.fury.io/js/express-longpoll) Lightweight long polling module for express.js with **TypeScript support**. ## Features - 🔄 **Simple API** - Easy to set up and use - 📡 **Promise-based** - Modern async/await support - 🎯 **TypeScript** - Full type definitions included - 🚀 **Production-ready** - Used by 147+ projects - 🔌 **Express Router** - Works with Express routers - 🎨 **Flexible** - Publish to specific users or broadcast to all ## Description Sets up basic long poll with subscribe and publish functionality. Perfect for real-time updates without WebSockets. ## Install ```bash npm install express-longpoll ``` ## Quick Start ### JavaScript ```javascript const express = require("express"); const app = express(); const longpoll = require("express-longpoll")(app); // Create endpoint await longpoll.create("/events"); // Publish data await longpoll.publish("/events", { message: "Hello!" }); ``` ### TypeScript ```typescript import express from "express"; import expressLongPoll from "express-longpoll"; const app = express(); const longpoll = expressLongPoll(app, { DEBUG: true }); await longpoll.create("/events", { maxListeners: 100 }); await longpoll.publish("/events", { message: "Hello!" }); ``` ## Usage **Basic initalization** ```javascript var express = require("express"); var app = express(); var longpoll = require("express-longpoll")(app); // You can also enable debug flag for debug messages var longpollWithDebug = require("express-longpoll")(app, { DEBUG: true }); ``` **Quick-start code** Server - server.js ```javascript var express = require("express"); var app = express(); var longpoll = require("express-longpoll")(app); // Creates app.get("/poll") for the long poll longpoll.create("/poll"); app.listen(8080, function () { console.log("Listening on port 8080"); }); var data = { text: "Some data" }; // Publishes data to all clients long polling /poll endpoint // You need to call this AFTER you make a GET request to /poll longpoll.publish("/poll", data); // Publish every 5 seconds setInterval(function () { longpoll.publish("/poll", data); }, 5000); ``` Client - index.js (with jQuery) ```javascript var poll = function () { $.ajax({ url: "localhost:8080/poll", success: function (data) { console.log(data); // { text: "Some data" } -> will be printed in your browser console every 5 seconds poll(); }, error: function () { poll(); }, timeout: 30000 // 30 seconds }); }; // Make sure to call it once first, poll(); ``` ### **longpoll.create(url, [options])** Sets up an express endpoint using the URL provided. ```javascript var longpoll = require("express-longpoll")(app); longpoll.create("/poll"); longpoll.create("/poll2", { maxListeners: 100 }); // set max listeners ``` **Options:** - `maxListeners` (number): Maximum number of listeners. Default: 0 (unlimited, disables EventEmitter warnings). Set to a specific number if you want to limit concurrent connections. Fixes Issue #12. ### **longpoll.create(url, middleware, [options])** Set up an express endpoint using the URL provided, and use middleware. ```javascript var longpoll = require("express-longpoll")(app); longpoll.create("/poll", function (req, res, next) { // do something next(); }); ``` ### **longpoll.publish(url, data)** Publishes `data` to all listeners on the `url` provided. ```javascript var express = require("express"); var app = express(); var longpoll = require("express-longpoll")(app); longpoll.create("/poll"); longpoll.publish("/poll", {}); longpoll.publish("/poll", { hello: "Hello World!" }); longpoll.publish("/poll", jsonData); ``` ### **longpoll.publishToId(url, id, data)** Publish data to a specific request. See [the basic example](./examples/basic) on how to use this effectively. ## Works with Routers ```javascript var express = require("express"); var router = express.Router(); // with router var longpoll = require("express-longpoll")(router); longpoll.create("/routerpoll"); router.get("/", (req, res) => { longpoll.publish("/routerpoll", { text: "Some data" }); res.send("Sent data!"); }); module.exports = router; ``` ## Can publish to any endpoint, from anywhere. **server.js** - create here ```javascript var longpoll = require("express-longpoll")(app); longpoll.create("/poll"); ``` **route.js** - use here ```javascript var longpoll = require("express-longpoll")(router); // Can publish to any endpoint longpoll.publish("/poll"); ``` ## Using Promises ```javascript longpoll .create("/poll") .then(() => { console.log("Created /poll"); }) .catch((err) => { console.log("Something went wrong!", err); }); longpoll .publish("/poll", data) .then(() => { console.log("Published to /poll:", data); }) .catch((err) => { console.log("Something went wrong!", err); }); ``` ## Sample clientside code to subscribe to the longpoll ### Client using jQuery ```javascript var subscribe = function (url, cb) { $.ajax({ method: "GET", url: url, success: function (data) { cb(data); }, complete: function () { setTimeout(function () { subscribe(url, cb); }, 1000); }, timeout: 30000 }); }; subscribe("/poll", function (data) { console.log("Data:", data); }); subscribe("/poll2", function (data) { console.log("Data:", data); }); ``` ## Live Demo Check out the **Collaborative Mouse Tracker** demo in the `examples/` folder - a stunning real-time application showcasing express-longpoll capabilities: - 🖱️ Real-time cursor tracking across multiple browser tabs ```bash cd examples/collaborative-mouse-tracker npm install npm start # Open http://localhost:3006 in multiple tabs ``` ## API Reference ### `longpoll.create(url, [middleware], [options])` Creates a long-poll endpoint. **Options:** - `maxListeners` (number): Maximum number of listeners. Default: 0 (unlimited, disables EventEmitter warnings). Set to a specific number if you want to limit concurrent connections. Fixes Issue #12. **Returns:** `Promise` ### `longpoll.publish(url, data)` Publishes data to all listeners on the endpoint. **Returns:** `Promise` ### `longpoll.publishToId(url, id, data)` Publishes data to a specific listener by ID. **Returns:** `Promise` ## Testing express-longpoll has comprehensive test coverage: ```bash npm test ``` **Test Results:** ``` express-longpoll - Additional Tests Error Handling ✔ should reject when creating duplicate URL ✔ should reject when publishing to non-existent URL ✔ should reject when publishing to ID on non-existent URL maxListeners Option ✔ should set maxListeners when option is provided ✔ should handle multiple concurrent connections with maxListeners Middleware Support ✔ should support middleware function ✔ should support middleware with options publishToId ✔ should publish to specific user ID Router Support ✔ should work with Express Router Promise API ✔ should resolve promise on successful create ✔ should resolve promise on successful publish ✔ should support async/await syntax Debug Mode ✔ should enable debug logging when DEBUG is true ✔ should not log when DEBUG is false Data Types ✔ should handle object data ✔ should handle array data ✔ should handle string data ✔ should handle null data express-longpoll longpoll.create(url, data) ✔ should create a .get express endpoint longpoll.publish(url, data) ✔ should publish data to all requests listening on a url ✔ should publish data to all clients requests listening on a url 21 passing (5s) ``` ## Best Practices - Set `maxListeners` to prevent memory leaks in production - Use `DEBUG: true` during development for helpful logs - Implement proper error handling with `.catch()` - Consider timeout values based on your use case (typically 30-60 seconds) ## Changelog See [CHANGELOG.md](./CHANGELOG.md) for version history. ## License ISC --- _Source: https://npm.io/package/express-longpoll · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._