Refactoring Advisor

Quick Start

Plan refactoring based on identified issues:

1. Identify the problem (code smell, complexity)
2. Select appropriate refactoring pattern
3. Create step-by-step plan
4. Ensure tests exist
5. Refactor incrementally

Instructions

Step 1: Assess Current State

Analyze the code:

• What is the problem? (long method, god class, etc.)
• What is the impact? (maintainability, testability)
• What is the risk? (how much code depends on it)

Step 2: Select Refactoring Strategy

Problem	Strategy	Risk
Long Method	Extract Method	Low
God Class	Extract Class	Medium
Duplicated Code	Extract Method	Low
Switch Statement	Replace with Polymorphism	High
Long Parameter List	Introduce Parameter Object	Medium

Step 3: Create Refactoring Plan

Template:

## Refactoring: [Name]

**Problem:** [Description]
**Goal:** [Desired outcome]
**Risk Level:** [Low/Medium/High]

### Prerequisites
- [ ] Tests exist and pass
- [ ] Code is committed
- [ ] Dependencies identified

### Steps
1. [First small change]
2. [Run tests]
3. [Next small change]
4. [Run tests]
...

### Validation
- [ ] All tests pass
- [ ] No functionality changed
- [ ] Code is cleaner

Step 4: Execute Incrementally

Golden Rule: Make the change easy, then make the easy change

1. Make one small change
2. Run tests
3. Commit
4. Repeat

Refactoring Examples

Extract Method

Before:

function printOwing(invoice) {
  let outstanding = 0;
  
  console.log("***********************");
  console.log("**** Customer Owes ****");
  console.log("***********************");
  
  for (const o of invoice.orders) {
    outstanding += o.amount;
  }
  
  console.log(`name: ${invoice.customer}`);
  console.log(`amount: ${outstanding}`);
}

Plan:

1. Extract banner printing
2. Run tests
3. Extract outstanding calculation
4. Run tests
5. Extract details printing
6. Run tests

After:

function printOwing(invoice) {
  printBanner();
  const outstanding = calculateOutstanding(invoice);
  printDetails(invoice, outstanding);
}

function printBanner() {
  console.log("***********************");
  console.log("**** Customer Owes ****");
  console.log("***********************");
}

function calculateOutstanding(invoice) {
  return invoice.orders.reduce((sum, o) => sum + o.amount, 0);
}

function printDetails(invoice, outstanding) {
  console.log(`name: ${invoice.customer}`);
  console.log(`amount: ${outstanding}`);
}

Extract Class

Before:

class Person {
  name;
  officeAreaCode;
  officeNumber;
  
  getTelephoneNumber() {
    return `(${this.officeAreaCode}) ${this.officeNumber}`;
  }
}

Plan:

1. Create TelephoneNumber class
2. Move areaCode field
3. Run tests
4. Move number field
5. Run tests
6. Move getTelephoneNumber method
7. Run tests
8. Update Person to use TelephoneNumber
9. Run tests

After:

class TelephoneNumber {
  areaCode;
  number;
  
  toString() {
    return `(${this.areaCode}) ${this.number}`;
  }
}

class Person {
  name;
  telephoneNumber;
  
  getTelephoneNumber() {
    return this.telephoneNumber.toString();
  }
}

Safety Checklist

Before refactoring:

• Tests exist and pass
• Code is in version control
• You understand what the code does
• You have time to complete the refactoring

During refactoring:

• Make small changes
• Run tests after each change
• Commit working states
• Don't add features while refactoring

After refactoring:

• All tests pass
• Code review completed
• Documentation updated
• No functionality changed