Integrate the SDK

Using the JavaScript SDK

With your new-feature flag created, bring it into your app with the JavaScript SDK.

Check out our other SDKs for Node.js, Next.js, React, and more.

Install the SDK

Install the SDK with your preferred package manager:

npm install @flagsync/js-sdk
npm install -D @flagsync/cli

yarn add @flagsync/js-sdk
yarn add -D @flagsync/cli

pnpm add @flagsync/js-sdk
pnpm add -D @flagsync/cli

Initialize the SDK

Create a client with your SDK key and a unique user identifier, such as user ID or email.

import { FlagSyncFactory } from '@flagsync/js-sdk';

const factory = FlagSyncFactory({
  sdkKey: 'your-sdk-key', // Replace with your SDK key
  core: {
    key: 'userId_0x123' // Unique identifier
  }
});

const client = factory.client();

Get your SDK key from your Workspace settings for the target Environment.

Wait for Readiness

Ensure the SDK is ready before checking flags:

await client.waitForReady();
console.log('SDK is ready!');

Evaluate Your Flag

Get the new-feature flag’s value:

const value = client.flag<boolean>('new-feature');
console.log(value);

Calling flag() automatically logs an impression, tracking which variant each user sees—vital for metrics later.

Putting it all together

Here’s the full example:

import { FlagSyncFactory } from '@flagsync/js-sdk';

const factory = FlagSyncFactory({
  sdkKey: 'your-sdk-key', // Replace with your SDK key
  core: {
    key: 'userId_0x123' // Unique identifier
  }
});

const client = factory.client();

await client.waitForReady();
console.log('SDK is ready!');

const value = client.flag<boolean>('new-feature');
console.log(value);

Next Steps

The SDK is ready—now track user actions:

Send events in Quickstart: Send Events.
Explore targeting in Targeting & Rollouts.
See other options in other SDKs

Send EventsTrack user actions in FlagSync to measure feature impact.

Getting Started

Feature Flags

Impressions

Events

Metrics

Experiments

Integrate the SDK

Using the JavaScript SDK

Next Steps

​Using the JavaScript SDK

​Next Steps

Using the JavaScript SDK

Next Steps