dont-repeat-yourself

To eliminate code duplication, you extract repeated logic blocks into reusable functions and shared utilities. This centralizes common code into single sources of truth, ensuring easier maintenance and preventing drift across files and modules.

The best way to refactor duplicated form validations is to extract the shared logic into a single reusable validator function. You then update all call sites to reference this centralized utility, ensuring consistent validation behavior across your project.

You should centralize shared logic during feature growth when identical code blocks start appearing across files, forms, or modules. Extracting these into reusable utilities prevents drift, lowers maintenance risk, and keeps your codebase clean as it scales.

You extract shared utilities by identifying repeated logic, moving it into a centralized function with a clear interface, and writing tests for the new utility. You then systematically update all existing call sites to use this single source of truth.

Duplicated code leads to higher maintenance risk because updates must be applied in multiple places, increasing the chance of drift. Centralizing common logic into reusable functions eliminates this repetition and ensures changes only need to be made once.