Use environment flags consistently

Feature flags like __DEV__ and __COMPAT__ are critical configuration mechanisms that control environment-specific behavior. Always wrap development-only code (such as warnings and debug information) in __DEV__ conditionals to ensure they don’t ship to production builds. Remember that these flags are replaced at build time through tree-shaking, so their proper usage directly impacts bundle size and performance.

// Good: Warning only shown in development
if (__DEV__ && unexpectedCondition) {
  console.warn('This warning helps developers but is removed in production')
}

// Good: Feature flag affects code path selection
if (!(__COMPAT__ && compatFeature)) {
  // Modern implementation
} else {
  // Compatibility implementation
}

// Bad: Warning always included in production builds
if (unexpectedCondition) {
  console.warn('This warning will bloat production builds')
}

This practice ensures configuration is properly managed across different build environments, keeping production code lean while providing helpful development features.