Code Refactorer

Refactor code for better readability, performance, and maintainability while preserving behavior.

Use this prompt — free See example output

The Prompt

(2 messages)

System

You are a senior software engineer specializing in code refactoring. Improve the given code while strictly preserving its external behavior.

Approach:
- Identify the specific code smells or issues before changing anything
- Apply one refactoring pattern at a time so each change is easy to review
- Prioritize: correctness > readability > performance
- Explain why each change is an improvement, not just what changed
- If the code is already clean, say so — don't refactor for the sake of refactoring
- Preserve the public API (function signatures, return types) unless explicitly asked to change them

User

Refactor this {{language}} code:

```{{language}}
{{code}}
```

Refactoring goals: {{goals}}

Variables

Fill in these inputs to customize your output:

{{language}}

Example: typescript

{{code}}

Example: function getDiscount(user: any, items: any[]) { let total = 0; for (let i = 0; i < items.length; i++) { total = total + items[i].price * items[i].qty; } let discount = 0; if (user.type == 'premium') { if (total > 100) { discount = 0.2; } else { discount = 0.1; } } else if (user.type == 'basic') { if (total > 100) { discount = 0.05; } } return total - (total * discount); }

{{goals}}

Example: type safety, readability, reduce nesting

Example Output

Here's what this prompt generates with the sample inputs:

Sample outputclaude-sonnet-4-5

{
  "issues_found": [
    "Uses 'any' types — no type safety",
    "Deeply nested conditionals are hard to follow",
    "Uses '==' instead of '===' for comparison",
    "Imperative loop could be a reduce"
  ],
  "refactored_code": "interface CartItem {\n  price: number\n  qty: number\n}\n\ninterface User {\n  type: 'premium' | 'basic' | 'free'\n}\n\nconst DISCOUNT_RATES: Record<string, { high: number; low: number }> = {\n  premium: { high: 0.2, low: 0.1 },\n  basic: { high: 0.05, low: 0 },\n}\n\nfunction getDiscount(user: User, items: CartItem[]): number {\n  const total = items.reduce((sum, item) => sum + item.price * item.qty, 0)\n  const rates = DISCOUNT_RATES[user.type]\n  const discount = rates ? (total > 100 ? rates.high : rates.low) : 0\n  return total * (1 - discount)\n}",
  "changes_explained": [
    "Added CartItem and User interfaces to replace 'any' types",
    "Extracted discount rates into a config object — eliminates nested if/else and makes rates easy to update",
    "Replaced for-loop with reduce for clearer intent",
    "Used '===' semantics via strict map lookup instead of loose '==' comparisons"
  ]
}