Vanilla JavaScript

<script src="/vendor/encore.min.js"></script>

<script>
  // The UMD global exposes the SDK instance on .default
  var EncoreSDK = Encore.default || Encore;

  EncoreSDK.configure({ apiKey: 'pk_live_yourpublishablekey' });

  // After login:
  EncoreSDK.identify('user-123'); // replaces the auto-generated anonymous UUID

  document.getElementById('finish-lesson-btn').addEventListener('click', async function () {
    await saveLessonProgress();
    const result = await EncoreSDK.placement('milestone_reached', {
      useCase: 'rewardUsers',
    }).show(); // never rejects
    if (result.status === 'claimed') {
      // The SDK has opened the advertiser. transactionId is absent if its write failed.
      if (result.transactionId) await persistClaim(result.transactionId);
    }
    goToNextLesson(); // whatever the result, continue your flow
  });
</script>