TypeScript enums are compiled into JavaScript objects, which means they have both numeric and string properties depending on how they’re defined. If enums aren’t used consistently or are passed between TypeScript and plain JavaScript, you might encounter runtime errors. For example, numeric enums might return unexpected values when accessed in JavaScript, or string enums might be evaluated differently in mixed TypeScript/JavaScript environments. To avoid these issues, ensure that enums are consistently defined and used across your codebase. In mixed environments, you might want to avoid enums altogether in favor of simpler constant values to ensure compatibility. By carefully managing how enums are used and transpiled, you can prevent runtime errors and ensure consistency between TypeScript and JavaScript.