Experiment Node.js SDK

initializeRemote(apiKey: string, config?: RemoteEvaluationConfig): RemoteEvaluationClient

import { Experiment } from '@amplitude/experiment-node-server';

const experiment = Experiment.initializeRemote('<DEPLOYMENT_KEY>', config: {
    fetchTimeoutMillis: 500,
    fetchRetries: 1,
    fetchRetryBackoffMinMillis: 0,
    fetchRetryTimeoutMillis: 500,
});

fetchV2(user: ExperimentUser, fetchOptions?: FetchOptions): Promise<Variants>

const user = {
    user_id: 'user@company.com',
    device_id: 'abcdefg',
    user_properties: {
        'premium': true,
    },
};
const variants = await experiment.fetchV2(user);

const variant = variants['YOUR-FLAG-KEY'];
if (variant?.value === 'on') {
    // Flag is on
} else {
    // Flag is off
}

initializeLocal(apiKey: string, config?: LocalEvaluationConfig): LocalEvaluationClient

start(): Promise<void>

await experiment.start();

evaluateV2(user: ExperimentUser, flagKeys?: string[], options?: EvaluateOptions): Record<string, Variant>

// The user to evaluate
const user = { device_id: 'abcdefg' };

// Evaluate all flag variants
const allVariants = experiment.evaluateV2(user);

// Evaluate a specific subset of flag variants
const specificVariants = experiment.evaluateV2(user, [
  'my-local-flag-1',
  'my-local-flag-2',
]);

const experiment = Experiment.initializeLocal('<DEPLOYMENT_KEY>', {
  // (Recommended) Enable local evaluation cohort targeting.
  cohortSyncConfig: {
    apiKey: '<API_KEY>',
    secretKey: '<SECRET_KEY>'
  }
});

import { Experiment, LogLevel, LoggerProvider } from '@amplitude/experiment-node-server';

class MyCustomLogger implements LoggerProvider {
  verbose(message, ...optionalParams) {
    // Implement verbose logging
  }

  debug(message, ...optionalParams) {
    // Implement debug logging
  }

  info(message, ...optionalParams) {
    // Implement info logging
  }

  warn(message, ...optionalParams) {
    // Implement warn logging
  }

  error(message, ...optionalParams) {
    // Implement error logging
  }
}

// Initialize with custom logger
const experiment = Experiment.initializeLocal(
  '<DEPLOYMENT_KEY>',
  {
    logLevel: LogLevel.Debug,
    loggerProvider: new MyCustomLogger()
  }
);

import { AmplitudeCookie } from '@amplitude/experiment-node-server';
import { v4 as uuidv4 } from 'uuid';
// Get the cookie name for the Amplitude API key
// For Browser SDK 2.0 cookies, pass true as second parameter:
// const ampCookieName = AmplitudeCookie.cookieName('amplitude-api-key', true);
const ampCookieName = AmplitudeCookie.cookieName('amplitude-api-key');
let deviceId = null;
// Try to get device ID from existing cookie
if (req.cookies[ampCookieName]) {
  deviceId = AmplitudeCookie.parse(req.cookies[ampCookieName]).device_id;
  // For Browser SDK 2.0: AmplitudeCookie.parse(req.cookies[ampCookieName], true).device_id;
}
// If no device ID found, generate a new one and set the cookie
if (!deviceId) {
  deviceId = uuidv4();
  const ampCookieValue = AmplitudeCookie.generate(deviceId);
  // For Browser SDK 2.0: AmplitudeCookie.generate(deviceId, true);
  res.cookie(ampCookieName, ampCookieValue, {
    domain: '.your-domain.com', // this should be the same domain used by the Amplitude JS SDK
    httpOnly: false,
    secure: false
  });
}