Registry / devops / featurehub-javascript-client-sdk

featurehub-javascript-client-sdk

library2.0.2jsnpmunverified

FeatureHub client/browser SDK for feature flags, remote configuration, and A/B testing. This package is designed for browser environments (or any non-Node.js context) and uses Server-Sent Events (SSE) for real-time updates. Version 2.0.2 requires Node >=20.0.0 and is TypeScript-first (ships types). Key differentiators: edge-compatible, supports catch-and-release mode for local feature flag overrides during development, integrates with React SDK via featurehub-react-sdk, and offers a client-side context for multi-environment support. Releases follow a monthly cadence.

devops web-framework http-networking

npm install featurehub-javascript-client-sdk

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · FEATUREHUB-JAVASCR

featurehub-javascript-client-sdk

devopsjavascriptv2.0.2

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

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

FeatureHubClient

✓ import { FeatureHubClient } from 'featurehub-javascript-client-sdk'

✗ const FeatureHubClient = require('featurehub-javascript-client-sdk')

ESM-only package; CommonJS require() will fail. TypeScript imports are identical.

FeatureHubContext

✓ import { FeatureHubContext } from 'featurehub-javascript-client-sdk'

Context helper for creating client instances with environment and user keys.

ClientFeatureRepository

✓ import { ClientFeatureRepository } from 'featurehub-javascript-client-sdk'

The main repository class that stores feature states and emits events.

Creates a FeatureHub client with a user context, starts receiving features via SSE, and checks a boolean flag after 5 seconds.

import { FeatureHubClient, ClientFeatureRepository } from 'featurehub-javascript-client-sdk'; const repository = new ClientFeatureRepository(); const apiKey = process.env.FEATUREHUB_API_KEY ?? ''; const client = FeatureHubClient.newClient({ apiKey, repository, // optional: if omitted, creates its own context: { // optional user context userKey: 'user123', // ... other attributes }, }).build(); // Listen for feature changes repository.addListener((features) => { console.log('Features updated:', features); }); // Start polling/SSE client.start(); // Get a boolean flag setTimeout(() => { const enabled = repository.isEnabled('my-feature-flag'); console.log('Feature enabled:', enabled); client.stop(); }, 5000);

Debug

Known issues

breakingIn v2.0.0, the client construction API changed from `new FeatureHubClient()` to `FeatureHubClient.newClient().build()`. Old instantiation will throw.

fix

Use the builder pattern: `FeatureHubClient.newClient({...}).build()`.

affects: <2.0.0

breakingThe package became ESM-only in v2.0.0. CommonJS `require()` throws 'ERR_REQUIRE_ESM'.

fix

Use `import` syntax or dynamic `import()` for CommonJS projects.

affects: >=2.0.0

gotcha`ClientFeatureRepository` events are not emitted until `client.start()` is called. Calling `repository.isEnabled()` before start returns `false` for all flags.

fix

Always call `client.start()` before reading features, or listen to the 'ready' event.

affects: >=1.0.0

gotchaThe `apiKey` must be a server-evaluated API key from FeatureHub; client-evaluated keys are not supported in this SDK (use the Node SDK instead).

fix

Ensure your FeatureHub environment is configured for server-side evaluation and use a server-sdk-api-key.

affects: >=1.0.0

Errors

Common errors & fixes

ERR_REQUIRE_ESM: require() of ES Module not supported

Using CommonJS require() on an ESM-only package (v2+)

fix

Switch to import syntax: `import { FeatureHubClient } from 'featurehub-javascript-client-sdk'`

TypeError: client.isEnabled is not a function

Calling isEnabled on the client object instead of the repository

fix

Use `repository.isEnabled('flag-key')` after setting up the repository on the client.

Error: No API key provided

Missing or empty `apiKey` in configuration

fix

Ensure you pass `apiKey` as a non-empty string to `newClient()`, e.g., `FeatureHubClient.newClient({ apiKey: '...' })`

Upgrade

Version history

2.0.2latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/featurehub-io/featurehub-javascript-sdk ↗

packagehttps://www.npmjs.com/package/featurehub-javascript-client-sdk ↗

homepagehttps://www.featurehub.io ↗