Example usage of the JavaScript (Browser) SDK

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

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Once you have installed an SDK, import the Optimizely Feature Experimentation library into your code, get your Optimizely Feature Experimentation 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:

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.
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.

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 via the customizable event dispatcher so we can count it in your Results page.

import { createInstance } from '@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
    user.trackEvent('purchased');
  }).catch((err) => {
    // handle error
  });
} else {
  // there was an error creating the instance, handle error
};

<html>

<head>
  <title>Hello world</title>
  <!-- Install Optimizely SDK -->
  <script src="https://unpkg.com/@optimizely/optimizely-sdk/dist/optimizely.browser.umd.min.js"></script>
  <!-- Add your datafile using your SDK key so you can later instantiate an Optimizely client -->
  <script src="https://cdn.optimizely.com/datafiles/<YOUR_SDK_KEY>.json/tag.js"></script>
</head>

<body>
  <h1>Hello world</h1>
</body>

<script>
  // instantiate an Optimizely client from the datafile
  var optimizelyClient = window.optimizelySdk.createInstance({
    datafile: window.optimizelyDatafile
  });
  if (optimizelyClient) {
    optimizelyClient.onReady().then(({ success, reason }) => {
      if (!success) {
        throw new Error(reason);
      }

      const attributes = { logged_in: true };
      const user = optimizelyClient.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
      user.trackEvent('purchased');
    }).catch((err) => {
      // handle error
    };
  } else {
    // there was an error creating the instance, handle error
  };
</script>

</html>

Updated 4 days ago