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Filtering Events

Control which events are sent to Syntropy.

beforeSend Hook​

The beforeSend hook is called before each event is sent:

Syntropy.init({
  projectId: 'your-project-id',
  beforeSend: (event) => {
    // Return the event to send it
    // Return null to drop it
    return event;
  },
});

Dropping Events​

By Error Message​

beforeSend: (event) => {
  const message = event.payload.message || '';
  
  // Drop common noise
  if (message.includes('ResizeObserver loop')) return null;
  if (message.includes('Script error')) return null;
  if (message.includes('Network request failed')) return null;
  
  return event;
}

By Error Type​

beforeSend: (event) => {
  // Only send error events
  if (event.type !== 'error') return null;
  return event;
}

By URL​

beforeSend: (event) => {
  const url = event.payload.url || window.location.href;
  
  // Don't track admin pages
  if (url.includes('/admin')) return null;
  
  // Don't track development
  if (url.includes('localhost')) return null;
  
  return event;
}

Modifying Events​

Scrub Sensitive Data​

beforeSend: (event) => {
  // Scrub passwords
  if (event.payload.extra?.password) {
    event.payload.extra.password = '[REDACTED]';
  }
  
  // Scrub credit cards
  if (event.payload.extra?.cardNumber) {
    event.payload.extra.cardNumber = '[REDACTED]';
  }
  
  // Scrub from breadcrumbs
  event.payload.breadcrumbs?.forEach(crumb => {
    if (crumb.data?.password) {
      crumb.data.password = '[REDACTED]';
    }
  });
  
  return event;
}

Add Context​

beforeSend: (event) => {
  // Add custom context
  event.payload.extra = {
    ...event.payload.extra,
    appVersion: APP_VERSION,
    buildTime: BUILD_TIME,
    featureFlags: getFeatureFlags(),
  };
  
  return event;
}

Normalize Errors​

beforeSend: (event) => {
  // Normalize error messages for better grouping
  if (event.payload.message) {
    // Remove variable parts
    event.payload.message = event.payload.message
      .replace(/user_\d+/g, 'user_XXX')
      .replace(/order_[a-f0-9]+/g, 'order_XXX');
  }
  
  return event;
}

Environment-Based Filtering​

Development​

Syntropy.init({
  projectId: 'your-project-id',
  enabled: process.env.NODE_ENV === 'production',
});

Specific Environments​

beforeSend: (event) => {
  // Don't send in staging
  if (process.env.NODE_ENV === 'staging') {
    return null;
  }
  return event;
}

Rate Limiting​

Use sampleRate to limit events:

Syntropy.init({
  projectId: 'your-project-id',
  sampleRate: 0.5, // Only send 50% of events
});

For more control:

let errorCount = 0;
const MAX_ERRORS_PER_MINUTE = 10;

setInterval(() => { errorCount = 0; }, 60000);

beforeSend: (event) => {
  if (event.type === 'error') {
    errorCount++;
    if (errorCount > MAX_ERRORS_PER_MINUTE) {
      return null; // Drop excess errors
    }
  }
  return event;
}