dry_skill

Overview

This skill helps developers eliminate duplicated logic across a TypeScript codebase by identifying repetition and guiding extraction into single, reusable units. It enforces the principle that each piece of knowledge or behavior should have one canonical representation. Use it to reduce maintenance cost, prevent divergence, and make fixes safer and faster.

How this skill works

The skill inspects code patterns that indicate copy-paste or repeated logic: identical functions, repeated regexes/validation, constants duplicated across files, and similar functions that differ only by small details. It recommends extracting shared functions, parameterizing differences, centralizing constants, or creating interfaces/base classes so the common behavior lives in one location and is reused everywhere.

When to use it

• You catch yourself copying and pasting code to handle a similar case
• Making the same bug fix or change in multiple files
• You see the same validation, regex, or calculation repeated
• Adding a new feature that duplicates existing logic
• Multiple functions share most of their body but differ in small ways

Best practices

• Extract the common behavior first, then reuse it in all callers
• Parameterize differences rather than duplicating whole functions
• Centralize constants and business rules in a single module
• Name extracted functions or modules clearly to improve readability
• Refactor small duplications immediately—tiny copies multiply

Example use cases

• Replace two email validators with a single validateEmail(email: string) function and reuse it across forms
• Move tax or pricing logic into calculateTax(price: number) and import it from cart, checkout, and invoice modules
• Extract shared formatting logic into formatName(person, suffix?) instead of separate formatUserName and formatAdminName
• Create a validators module when identical validation patterns appear across multiple components
• Centralize shared constants (TAX_RATE, API_ENDPOINTS) to avoid inconsistent values