SDK

The official TypeScript / JavaScript client for ftflg.

Install

npm install ftflg

Initialize

Create one client per application. Pass static context at init time; update it later with setContext().

import { Ftflg } from 'ftflg';

const flags = new Ftflg({
  apiKey: 'ff_your_api_key',
  baseUrl: 'https://your-ftflg-instance.com',
  context: {
    app_version: '2.5.0',
    country: 'DE',
  },
});

Option	Required	Description
apiKey	yes	Your project API key from the ftflg dashboard.
baseUrl	yes	Base URL of your ftflg instance.
context	no	Initial context key-value pairs. Can be updated at runtime.

Evaluate a flag

Call eval(flagKey) to get the current state. Always guard against null values.

const result = await flags.eval('dark_mode');

if (result.enabled) {
  applyTheme(result.value ?? '#1a1a2e');
}

// Evaluate multiple flags at once:
const [checkout, banner] = await Promise.all([
  flags.eval('new_checkout'),
  flags.eval('maintenance_banner'),
]);

Return type

interface EvalResult {
  enabled: boolean;
  value: string | null;
}

Field	Description
enabled	true if all enabled rules passed (or flag has no rules and is enabled).
value	The string value attached to the flag, or null if disabled / rules failed.

Raw HTTP (no SDK)

Any language can call the eval endpoint directly. Every body key except api_key is treated as context.

curl -X POST https://your-ftflg-instance.com/eval/dark_mode \
  -H 'Content-Type: application/json' \
  -d '{
    "api_key": "ff_your_api_key",
    "country": "DE",
    "app_version": "2.5.0"
  }'

# Response:
# { "enabled": true, "value": "#1a1a2e" }