Set up Node.js (server-side) SDK

import * as LaunchDarkly from '@launchdarkly/node-server-sdk';
// This is your LaunchDarkly SDK key.
// Never hardcode your SDK key in production.
const client = LaunchDarkly.init('YOUR_SDK_KEY');
client.once('ready', function () {
  // For onboarding purposes only we flush events as soon as
  // possible so we quickly detect your connection.
  // You don't have to do this in practice because events are automatically flushed.
  client.flush();
  console.log('SDK successfully initialized!');
});