JavaScript quickstart

1. Install hypertune

Once you have a JavaScript application ready, install Hypertune's JavaScript SDK:

npm

npm install hypertune

yarn

pnpm

2. Set environment variables

Define the following environment variables in your .env file:

.env

HYPERTUNE_TOKEN=token
HYPERTUNE_OUTPUT_DIRECTORY_PATH=src/generated

Replace token with your main project token which you can find in the Settings tab of your project.

3. Generate the client

Generate a type-safe client to access your flags by running:

npm

npx hypertune

yarn

pnpm

4. Use the client

Install the dotenv package or ensure you have another way to load environment variables:

npm

npm install dotenv
npm install -D @types/dotenv

yarn

pnpm

Add a new file called loadEnv.ts that loads environment variables with dotenv:

src/lib/loadEnv.ts

import * as dotenv from "dotenv";

dotenv.config();

Add a new file called getHypertune.ts that exports a getHypertune function:

src/lib/getHypertune.ts

import { createSource } from '../generated/hypertune'

const hypertuneSource = createSource({
  token: process.env.HYPERTUNE_TOKEN!,
})

export default async function getHypertune() {
  await hypertuneSource.initIfNeeded()

  return hypertuneSource.root({
    args: {
      context: {
        environment:
          process.env.NODE_ENV === 'development'
            ? 'development'
            : 'production',
        user: {
          id: 'e23cc9a8-0287-40aa-8500-6802df91e56a',
          name: 'Example User',
          email: '[email protected]',
        },
      },
    },
  })
}

To access flags, use the getHypertune function:

src/index.ts

import './lib/loadEnv'
import getHypertune from './lib/getHypertune'

async function main() {
  const hypertune = await getHypertune()

  const exampleFlag = hypertune.exampleFlag({ fallback: false })

  console.log(`Example Flag: ${exampleFlag}`)
}

main()

If you have a Content Security Policy, add the following to your connect-src directive: https://edge.hypertune.com https://gcp.fasthorse.workers.dev. This enables reporting of flag evaluations, experiment exposures, and analytics events.

5. (Optional) Include a build-time snapshot

To improve reliability, you can include a snapshot of your flag logic in the generated client at build time. The SDK will instantly initialize from the snapshot first before fetching the latest flag logic from Hypertune Edge.

Add the following environment variable to your .env file:

HYPERTUNE_INCLUDE_INIT_DATA=true

Then regenerate the client.

You can keep the snapshot fresh by setting up a webhook to regenerate the client on every Hypertune commit. In this case, you don't need to initialize from Hypertune Edge at all, eliminating network latency and bandwidth, improving both performance and efficiency.

Next steps

Now you can update the logic for exampleFlag from the Hypertune UI without updating your code or waiting for a new build, deployment, app release, or service restart.

To add a new flag, create it in the Hypertune UI then regenerate the client.