cometd

library9.0.0jsnpmunverified

CometD is a scalable comet and WebSocket messaging library for web applications, providing publish/subscribe, RPC, and peer-to-peer communication patterns. The current stable version is 9.0.0, released under the Apache 2.0 license. It ships TypeScript types and supports ES modules. CometD replaces the older cometd-jQuery and provides a modern, promise-based API. It differentiates from alternatives like Socket.IO by being more lightweight and focusing on the Bayeux protocol with built-in support for long-polling, WebSocket, and extensions like time-stamping.

messaging

npm install cometd

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · COMETD

cometd

messagingjavascriptv9.0.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

CometD

✓ import { CometD } from 'cometd'

✗ const CometD = require('cometd').CometD

CommonJS require is not supported in the ES module distribution. Use named import.

TimeStampExtension

✓ import { TimeStampExtension } from 'cometd/TimeStampExtension'

✗ import TimeStampExtension from 'cometd/TimeStampExtension'

TimeStampExtension is a named export, not default. Use named import syntax.

default import (assuming no default export)

✓ import { CometD } from 'cometd'

✗ import CometD from 'cometd'

There is no default export; always use named imports.

Initializes a CometD client, registers a time-stamp extension, configures the URL, performs a handshake, and subscribes to a topic.

import { CometD } from 'cometd'; import { TimeStampExtension } from 'cometd/TimeStampExtension'; const cometd = new CometD(); cometd.registerExtension('timestamp', new TimeStampExtension()); cometd.configure({ url: process.env.COMETD_URL ?? 'http://localhost:8080/cometd' }); cometd.handshake((reply) => { if (reply.successful) { console.log('Handshake succeeded'); cometd.subscribe('/topic', (message) => { console.log('Received message:', message.data); }); } });

Debug

Known issues

breakingVersion 9 drops support for older browser APIs and requires ES module environment.

fix

Ensure your runtime supports ES modules (Node >=13.2 or modern browser). Use import/export syntax.

affects: >=9.0.0

deprecatedThe cometd-jQuery integration module is deprecated and removed in v9.

fix

Use the core CometD library without jQuery. Migrate any jQuery-specific extensions.

affects: >=9.0.0

breakingCommonJS require() no longer works starting from v8.0.0.

fix

Switch to ES module imports: import { CometD } from 'cometd'.

affects: >=8.0.0

gotchaImport paths for extensions are case-sensitive and must use forward slashes.

fix

Use correct path like 'cometd/TimeStampExtension' not 'cometd/timestamp'.

affects: >=8.0.0

Errors

Common errors & fixes

Uncaught TypeError: cometd.configure is not a function

CometD object not properly imported (default import used instead of named import).

fix

Use named import: import { CometD } from 'cometd';

Cannot find module 'cometd'

Package not installed or import path incorrect in CommonJS environment.

fix

Install package via npm install cometd and ensure using ES module syntax.

Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of ...

Server misconfigured to serve .js files with incorrect MIME type for ES modules.

fix

Configure server to serve .js files with MIME type application/javascript or text/javascript.

Upgrade

Version history

9.0.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

29 hits · last 30 days

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OpenAI (training)

Resources

githubhttps://github.com/cometd/cometd-javascript ↗

packagecometd ↗

homepagehttps://cometd.org ↗