unleash-node-sdk

The official Unleash SDK for Node.js. This SDK lets you evaluate feature flags in your Node.js services and applications.

Unleash is an open-source feature management platform. You can use this SDK with Unleash Enterprise or Unleash Open Source.

For complete documentation, see the Node.js SDK reference.

Requirements

• Node.js 20 or later

Installation

npm install unleash-client

Quick start

The following example initializes the SDK and checks a feature flag:

import { startUnleash } from 'unleash-client';

const unleash = await startUnleash({
  url: 'https://<your-unleash-instance>/api/',
  appName: 'my-node-name',
  customHeaders: { Authorization: '<your-backend-token>' },
});

const enabled = unleash.isEnabled('my-feature');
if (enabled) {
  // new behavior
}

const variant = unleash.getVariant('checkout-experiment');
if (variant.name === 'blue') {
  // blue variant behavior
} else if (variant.name === 'green') {
  // green variant behavior
}

Contributing

Local development

Clone the repository and install dependencies:

git clone https://github.com/Unleash/unleash-node-sdk.git
cd unleash-node-sdk
yarn install

The client specification test data is included as a dev dependency (@unleash/client-specification). It defines a shared contract that all Unleash SDKs test against.

Running tests

yarn test        # run tests
yarn coverage    # run tests with coverage

Benchmarking

Run the feature flag evaluation benchmark:

yarn bench:isEnabled

Code style and formatting

The project uses Biome for linting and formatting:

yarn lint        # check for issues
yarn lint:fix    # auto-fix issues

Building

yarn build       # compile TypeScript to lib/

License

Apache-2.0