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Example usage of the JavaScript (Node) SDK

A code example of how to use the Optimizely Feature Experimentation JavaScript (Node) SDK to evaluate feature flags, activate A/B tests, or feature tests.

Once you have installed the JavaScript (Node) SDK, import the Optimizely Feature Experimentation library into your code, get your project's datafile, and instantiate a client. Then, you can use the client to evaluate flag rules, including A/B tests and flag deliveries.

This example demonstrates the basic usage of each of these concepts:

  1. Evaluate a flag with the key product_sort using the Decide method. As a side effect, the Decide function also sends a decision event to Optimizely Feature Experimentation to record that the current user has been exposed to the experiment.

  2. Conditionally execute your feature code. You have a couple of options:

  • Fetch the flag enabled state, then check a configuration variable on the flag called sort_method. The SDK evaluates your flag rules and determines what flag variation the user is in, and therefore which sort method variable they should see.
  • Fetch on the flag variation, then run 'control' or 'treatment' code.
  1. Use event tracking to track an event called purchased. This conversion event measures the impact of an experiment. Using the Track Event method, the purchase is automatically attributed back to the running A/B test for which we made a decision, and the SDK sends a network request to Optimizely Feature Experimentation through the customizable event dispatcher so Optimizely can count it in your results page.
const { createInstance } = require('@optimizely/optimizely-sdk');

const optimizely = createInstance({
  sdkKey: '<YOUR_SDK_KEY>' // Provide the sdkKey of your desired environment here

if (optimizely) {
  optimizely.onReady().then(({ success, reason }) => {
    if (!success) {
      throw new Error(reason);

    const attributes = { logged_in: true };
    const user = optimizely.createUserContext('user123', attributes);

    if (!user) {
      throw new Error('failed to create user context');

    const decision = user.decide('product_sort');
    const variationKey = decision['variationKey'];

    if (variationKey === null) {
      console.log(' decision error: ', decision['reasons']);

    const enabled = decision['enabled'];

    if (enabled) {
      const sortMethod = decision.variables['sort_method'];
      // execute code for sort method value

    if (variationKey === 'control') {
      // Execute code for control constiation
    } else if (variationKey === 'treatment') {
      // Execute code for treatment constiation

    // Track an event
  }).catch((err) => {
    // handle error
} else {
  // there was an error creating the instance, handle error