feature-flags-sdk

SDK for consuming feature flags in Node.js and React apps.

Backed by feature-flags-core.

Install

npm install feature-flags-sdk

For React usage:

npm install react react-dom

Node / Server Usage

import { isFeatureEnabled } from "feature-flags-sdk"

if (isFeatureEnabled("newAPI")) {
  console.log("Using new API")
}

You can also use:

• readFlags(cwd?)
• writeFlags(flags, cwd?)
• evaluateFlags(keys, cwd?)
• fetchRemoteFlags(url, init?)
• FLAG_FILENAME, getFlagFilePath(cwd?)

React Usage

import { useFeature } from "feature-flags-sdk/react"

export default function App() {
  const newUI = useFeature("newUI")
  return newUI ? <h1>New UI</h1> : <h1>Old UI</h1>
}

useFeature(key, options?)

Options:

• remoteUrl (default: "/.featureflags.json")
• pollIntervalMs (default: 400)

The hook polls a JSON endpoint in the browser. Serve your flag file at that URL from your dev server or backend.

Example: custom endpoint

const beta = useFeature("betaCheckout", {
  remoteUrl: "/api/feature-flags",
  pollIntervalMs: 1000,
})