Code Refactoring

Refactoring Principles

When to Refactor

• Before adding new features (make change easy, then make easy change)
• After getting tests passing (red-green-refactor)
• When you see code smells
• During code review feedback

When NOT to Refactor

• Without tests covering the code
• Under tight deadlines with no safety net
• Code that will be replaced soon
• When you don't understand what the code does

Common Code Smells

Long Methods

// BEFORE: Method doing too much
function processOrder(order: Order) {
  // 100 lines of validation, calculation, notification, logging...
}

// AFTER: Extract into focused methods
function processOrder(order: Order) {
  validateOrder(order);
  const total = calculateTotal(order);
  saveOrder(order, total);
  notifyCustomer(order);
}

Deeply Nested Conditionals

// BEFORE: Arrow code
function getDiscount(user: User, order: Order) {
  if (user) {
    if (user.isPremium) {
      if (order.total > 100) {
        if (order.items.length > 5) {
          return 0.2;
        }
      }
    }
  }
  return 0;
}

// AFTER: Early returns (guard clauses)
function getDiscount(user: User, order: Order) {
  if (!user) return 0;
  if (!user.isPremium) return 0;
  if (order.total <= 100) return 0;
  if (order.items.length <= 5) return 0;
  return 0.2;
}

Primitive Obsession

// BEFORE: Primitives everywhere
function createUser(name: string, email: string, phone: string) {
  if (!email.includes('@')) throw new Error('Invalid email');
  // more validation...
}

// AFTER: Value objects
class Email {
  constructor(private value: string) {
    if (!value.includes('@')) throw new Error('Invalid email');
  }
  toString() { return this.value; }
}

function createUser(name: string, email: Email, phone: Phone) {
  // Email is already validated
}

Feature Envy

// BEFORE: Method uses another object's data extensively
function calculateShipping(order: Order) {
  const address = order.customer.address;
  const weight = order.items.reduce((sum, i) => sum + i.weight, 0);
  const distance = calculateDistance(address.zip);
  return weight * distance * 0.01;
}

// AFTER: Move method to where the data is
class Order {
  calculateShipping() {
    return this.totalWeight * this.customer.shippingDistance * 0.01;
  }
}

Refactoring Techniques

Extract Method

// Identify a code block that does one thing
// Move it to a new method with a descriptive name
// Replace original code with method call

function printReport(data: ReportData) {
  // Extract this block...
  const header = `Report: ${data.title}\nDate: ${data.date}\n${'='.repeat(40)}`;
  console.log(header);

  // ...into a method
  printHeader(data);
}

Replace Conditional with Polymorphism

// BEFORE: Switch on type
function getArea(shape: Shape) {
  switch (shape.type) {
    case 'circle': return Math.PI * shape.radius ** 2;
    case 'rectangle': return shape.width * shape.height;
    case 'triangle': return shape.base * shape.height / 2;
  }
}

// AFTER: Polymorphic classes
interface Shape {
  getArea(): number;
}

class Circle implements Shape {
  constructor(private radius: number) {}
  getArea() { return Math.PI * this.radius ** 2; }
}

class Rectangle implements Shape {
  constructor(private width: number, private height: number) {}
  getArea() { return this.width * this.height; }
}

Introduce Parameter Object

// BEFORE: Too many parameters
function searchProducts(
  query: string,
  minPrice
how to use code-refactoring
CursorClaude CodeClineCodexWindsurfGooseGitHub CopilotVS CodeGemini CLIKiloOpencodeKimi CLIRoo ClineAiderContinueZedBolt.newLovablev0Replit AgentSweepSmol DeveloperDevinCavemanAmpAntigravity
How to use code-refactoring on Cursor
AI-first code editor with Composer
1
Prerequisites
Before installing skills in Cursor, ensure your development environment meets these requirements:
›Cursor installed and configured on your development machine
›Node.js version 16.0+ with npm package manager (verify with node --version)
›Active project directory or workspace where you want to add code-refactoring
2
Execute installation command
Execute the skills CLI command in your project's root directory to begin installation:
$npx skills add https://github.com/skillcreatorai/ai-agent-skills --skill code-refactoringcopy
The skills CLI fetches code-refactoring from GitHub repository skillcreatorai/ai-agent-skills and configures it for Cursor.
3
Select Cursor when prompted
The CLI will show a list of available agents. Use arrow keys to navigate and space to select Cursor:
◆ Which agents do you want to install to?
│
│ ── Universal (.agents/skills) ── always included ────
│   • Amp
│   • Antigravity
│   • Cline
│   • Codex
│ ●Cursor(selected)
│   • Cursor
│   • Windsurf
4
Verify installation
Confirm successful installation by checking the skill directory location:
.cursor/skills/code-refactoring
Reload or restart Cursor to activate code-refactoring. Access the skill through slash commands (e.g., /code-refactoring) or your agent's skill management interface.
⚠
Security & Verification Notice
We perform automated surface-level scans (Gen AI Scanner, Socket, Snyk) during installation. These checks detect common vulnerabilities but do not guarantee complete security. Always review skill source code and verify the publisher's reputation before production use.
Skills execute code in your development environment. Always verify the publisher's identity, review recent commits, and test in isolated environments before production deployment.
Additional Resources
›View source code on GitHub›Skills CLI documentation›Learn more about Cursor›What are agent skills?