Using Flagonic from JavaScript

Flagonic has no JavaScript SDK of its own — by design. You use the official OpenFeature SDKs with their official OFREP providers. There are two flavors: the server SDK for Node services and the web SDK for browsers. Nothing Flagonic-specific ever enters your bundle, so swapping flag vendors later is a config change, not a refactor.

Prerequisites

• A running Flagonic server with a flag defined — see the overview & quickstart.
• An SDK key (fgn_sdk_…) for your project + environment.

Node services (server SDK)

npm install @openfeature/server-sdk @openfeature/ofrep-provider

Initialize once at startup; evaluations are per-request against Flagonic:

import { OpenFeature } from '@openfeature/server-sdk';
import { OFREPProvider } from '@openfeature/ofrep-provider';

await OpenFeature.setProviderAndWait(
  new OFREPProvider({
    baseUrl: process.env.FLAGONIC_URL,  // e.g. https://flags.example.com
    headers: [['Authorization', `Bearer ${process.env.FLAGONIC_SDK_KEY}`]],
  }),
);

const client = OpenFeature.getClient('checkout-service');

// per request:
const enabled = await client.getBooleanValue('new-checkout', false, {
  targetingKey: user.id,   // stable per subject — keeps rollouts sticky
  plan: user.plan,
});

All four flag types are available: getBooleanValue, getStringValue, getNumberValue, getObjectValue — each takes a default returned on any failure, so outages degrade gracefully.

Browsers (web SDK)

npm install @openfeature/web-sdk @openfeature/ofrep-web-provider

The web provider works differently: it fetches all flags for the current user in one OFREP bulk call (cheap re-checks via ETag), then evaluations are synchronous and instant. Set the evaluation context up front and again whenever the user changes:

import { OpenFeature } from '@openfeature/web-sdk';
import { OFREPWebProvider } from '@openfeature/ofrep-web-provider';

await OpenFeature.setContext({ targetingKey: user.id, plan: user.plan });
await OpenFeature.setProviderAndWait(
  new OFREPWebProvider({
    baseUrl: 'https://flags.example.com',
    headers: [['Authorization', `Bearer ${FLAGONIC_SDK_KEY}`]],
    pollInterval: 30000,  // re-check for flag changes every 30s
  }),
);

const client = OpenFeature.getClient();
const enabled = client.getBooleanValue('new-checkout', false); // sync

Inspect why a value was served

const details = await client.getBooleanDetails('new-checkout', false, ctx);
console.log(details.value, details.variant, details.reason);
// true "on" "TARGETING_MATCH" — other reasons: SPLIT, DEFAULT, STATIC, DISABLED, ERROR

Switching vendors

Both providers speak standard OFREP. Point baseUrl at any other OFREP-compatible backend and you're done — that's the whole Flagonic deal.