Refactoring with GitHub Copilot: A Developer’s Perspective

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Refactoring is like tidying up your workspace — it’s not glamorous, but it makes everything easier to work with. It’s the art of changing your code without altering its behavior, focusing purely on making it cleaner, more maintainable, and easier for developers (current and future) to understand. And in this day and age, we have a nifty assistant to make this process smoother: GitHub Copilot.

In this post, I’ll walk you through how GitHub Copilot can assist with refactoring, using a few straightforward examples in JavaScript. Whether you’re consolidating redundant code, simplifying complex logic, or breaking apart monolithic functions, Copilot can help you identify patterns, suggest improvements, and even write some of the boilerplate for you.

Starting Simple: Merging Redundant Functions

Let’s start with a basic example of refactoring to warm up. Imagine you’re handed a file with two nearly identical functions:

function foo() {
  console.log("foo");
}

function bar() {
  console.log("bar");
}

foo();
bar();

At first glance, there’s nothing technically wrong here — the code works fine, and the output is exactly as expected:

foo
bar

But as developers, we’re trained to spot redundancy. These functions have similar functionality; the only difference is the string they log. This is a great opportunity to refactor.

Here’s where Copilot comes into play. Instead of manually typing out a new consolidated function, I can prompt Copilot to assist by starting with a more generic structure:

function displayString(message) {
  console.log(message);
}

With Copilot’s suggestion for the function and a minor tweak to the calls, our refactored code becomes:

function displayString(message) {
  console.log(message);
}

displayString("foo");
displayString("bar");

The output remains unchanged:

foo
bar

But now, instead of maintaining two functions, we have one reusable function. The file size has shrunk, and the code is easier to read and maintain. This is the essence of refactoring — the code’s behavior doesn’t change, but its structure improves significantly.

Refactoring for Scalability: From Hardcoding to Dynamic Logic

Now let’s dive into a slightly more involved example. Imagine you’re building an e-commerce platform, and you’ve written a function to calculate discounted prices for products based on their category:

function applyDiscount(productType, price) {
  if (productType === "clothing") {
    return price * 0.9;
  } else if (productType === "grocery") {
    return price * 0.8;
  } else if (productType === "electronics") {
    return price * 0.85;
  } else {
    return price;
  }
}

console.log(applyDiscount("clothing", 100)); // 90
console.log(applyDiscount("grocery", 100));  // 80

This works fine for a few categories, but imagine the business adds a dozen more. Suddenly, this function becomes a maintenance headache. Hardcoding logic is fragile and hard to extend. Time for a refactor.

Instead of writing this logic manually, I can rely on Copilot to help extract the repeated logic into a reusable structure. I start by typing the intention:

function getDiscountForProductType(productType) {
  const discounts = {
    clothing: 0.1,
    grocery: 0.2,
    electronics: 0.15,
  };

  return discounts[productType] || 0;
}

Here, Copilot automatically fills in the logic for me based on the structure of the original function. Now I can refactor applyDiscount to use this helper function:

function applyDiscount(productType, price) {
  const discount = getDiscountForProductType(productType);
  return price - price * discount;
}

The behavior is identical, but the code is now modular, readable, and easier to extend. Adding a new category no longer requires editing a series of else if statements; I simply update the discounts object.

Refactoring with an Eye Toward Extensibility

A good refactor isn’t just about shrinking code — it’s about making it easier to extend in the future. Let’s add another layer of complexity to our discount example. What if we need to display the discount percentage to users, not just calculate the price?

Instead of writing separate hardcoded logic for that, I can reuse the getDiscountForProductType function:

function displayDiscountPercentage(productType) {
  const discount = getDiscountForProductType(productType);
  return `${discount * 100}% off`;
}

console.log(displayDiscountPercentage("clothing")); // "10% off"
console.log(displayDiscountPercentage("grocery"));  // "20% off"

By structuring the code this way, we’ve separated concerns into clear, modular functions:

• getDiscountForProductType handles the core data logic.

• applyDiscount uses it for price calculation.

• displayDiscountPercentage uses it for user-facing information.

With Copilot, this process becomes even faster — it anticipates repetitive patterns and can suggest these refactors before you even finish typing.

Code Smells: Sniffing Out the Problems in Your Codebase

If refactoring is the process of cleaning up your code, then code smells are the whiff of trouble that alerts you something isn’t quite right. A code smell isn’t necessarily a bug or an error—it’s more like that subtle, lingering odor of burnt toast in the morning. The toast is technically edible, but it might leave a bad taste in your mouth. Code smells are signs of potential problems, areas of your code that might function perfectly fine now but could morph into a maintenance nightmare down the line.

One classic example of a code smell is the long function. Picture this: you open a file and are greeted with a function that stretches on for 40 lines or more, with no break in sight. It might validate inputs, calculate prices, apply discounts, send emails, and maybe even sing “Happy Birthday” to the user if it has time. Sure, it works, but every time you come back to it, you feel like you’re trying to untangle Christmas lights from last year. This is not a good use of anyone’s time.

Let’s say you have a function in your e-commerce application that processes an order. It looks something like this:

function processOrder(order) {
  if (!validateOrder(order)) {
    return { success: false, error: "Invalid order" };
  }

  const totalPrice = calculateTotalPrice(order);
  const shippingCost = applyShipping(totalPrice);
  const finalPrice = totalPrice + shippingCost;

  sendOrderNotification(order);

  return { success: true, total: finalPrice };
}

Now, this is fine for a small project. It’s straightforward, gets the job done, and even has some comments in case your future self forgets what you were doing. But here’s the thing: this function is doing too much. It’s responsible for validation, pricing, shipping, and notifications, which are all distinct responsibilities. And if you were to write unit tests for this function, you’d quickly realize the pain of having to mock all these operations in one giant monolithic test.

Refactoring is the natural response to a code smell like this. The first step? Take a deep breath and start breaking things down. You could extract the validation logic, for example, into a separate function:

function validateOrder(order) {
  // Validation logic
  return order.items && order.items.length > 0;
}

With that in place, the processOrder function becomes simpler and easier to read:

function processOrder(order) {
  if (!validateOrder(order)) {
    return { success: false, error: "Invalid order" };
  }

  const totalPrice = calculateTotalPrice(order);
  const shippingCost = applyShipping(totalPrice);
  const finalPrice = totalPrice + shippingCost;

  sendOrderNotification(order);

  return { success: true, total: finalPrice };
}

That’s the beauty of refactoring—it’s like untangling those Christmas lights one loop at a time. The functionality hasn’t changed, but you’ve cleared up the clutter, making it easier for yourself and others to reason about the code.

Refactoring Strategies: Making the Codebase a Better Place

Refactoring is more than just cleaning up code smells. It’s about thinking strategically, looking at the long-term health of your codebase, and asking yourself, “How can I make this code easier to understand and extend?”

One of the most satisfying refactoring strategies is composing methods—taking large, unwieldy functions and breaking them into smaller, single-purpose methods. The processOrder example above is just the beginning. You can keep going by breaking out more logic, like the price calculation:

function calculateTotalPrice(order) {
  return order.items.reduce((total, item) => total + item.price, 0);
}

function applyShipping(totalPrice) {
  return totalPrice > 50 ? 0 : 5;
}

Each of these smaller functions has one responsibility and is easier to test in isolation. If the shipping rules change tomorrow, you only need to touch the applyShipping function, not the entire processOrder logic. This approach doesn’t just make your life easier—it creates code that can adapt to change without a cascade of unintended consequences.

Another common refactoring strategy is removing magic numbers—those cryptic constants that are scattered throughout your code like tiny landmines. Numbers like 50 in the shipping calculation or 0.9 in the discount example might make sense to you now, but future-you (or your poor colleague) will have no idea why they were chosen. Instead, extract them into meaningful constants:

const FREE_SHIPPING_THRESHOLD = 50;

function applyShipping(totalPrice) {
  return totalPrice > FREE_SHIPPING_THRESHOLD ? 0 : 5;
}

Now the intent is clear, and the code is easier to maintain. If the free shipping threshold changes to 60, you know exactly where to update it.

The Art of Balancing Refactoring with Reality

Here’s the thing about refactoring: it’s not just about following rules or tidying up for the sake of it. It’s about balancing effort and benefit. Not every piece of messy code is worth refactoring, and not every refactor is worth the time it takes. This is where tools like GitHub Copilot come into play.

Copilot doesn’t just suggest code—it suggests possibilities. You can ask it questions like, “How can I make this code easier to extend?” or “What parts of this file could be refactored?” and it will provide ideas. Sometimes those ideas are spot on, like extracting a repetitive block of logic into a helper function. Other times, Copilot might miss the mark or suggest something you didn’t need—but that’s part of the process. You’re still the one in charge.

One of the most valuable things Copilot can do is help you spot patterns in your codebase. Maybe you didn’t realize you’ve written the same validation logic in three different places. Maybe it points out that your processOrder function could benefit from splitting responsibilities into separate classes. These suggestions save you time and let you focus on the bigger picture: writing code that is clean, clear, and maintainable.

The Art of Refactoring: Simplifying Complexity with Clean Code and Design Patterns

As codebases grow, they tend to become like overgrown gardens—what started as neat and tidy often spirals into a chaotic mess of tangled logic and redundant functionality. This is where the true value of refactoring lies: it’s the art of pruning that overgrowth to reveal clean, elegant solutions without altering the functionality. But how do we take a sprawling codebase and turn it into something manageable? How do we simplify functionality, adopt clean code principles, and apply design patterns to improve both the current and future state of the code? Let’s dive in.

Simplifying Functionality: A Journey from Chaos to Clarity

Imagine you’re maintaining a large JavaScript application, and you stumble upon a class that handles blog posts. The class is tightly coupled to an Author class, accessing its properties directly to format author details for display. At first glance, it works fine, but this coupling is a ticking time bomb. The BlogPost class has a bad case of feature envy—it’s way too interested in the internals of the Author class. This isn’t just a code smell; it’s an opportunity to refactor.

Initially, you might be tempted to move the logic for formatting author details into a new method inside the Authorclass. That’s a solid first step:

class Author {
  constructor(name, bio) {
    this.name = name;
    this.bio = bio;
  }

  getFormattedDetails() {
    return `${this.name} - ${this.bio}`;
  }
}

class BlogPost {
  constructor(author, content) {
    this.author = author;
    this.content = content;
  }

  display() {
    return `${this.author.getFormattedDetails()}: ${this.content}`;
  }
}

Here, the getFormattedDetails method centralizes the responsibility of formatting author details inside the Author class. While this improves the code, it still assumes a single way to display author details, which can become limiting if the requirements change.

To simplify further and prepare for future flexibility, you might introduce a dedicated display class:

class AuthorDetailsFormatter {
  format(author) {
    return `${author.name} - ${author.bio}`;
  }
}

class BlogPost {
  constructor(author, content, formatter) {
    this.author = author;
    this.content = content;
    this.formatter = formatter;
  }

  display() {
    return `${this.formatter.format(this.author)}: ${this.content}`;
  }
}

By separating the formatting logic into its own class, you’ve decoupled the blog post from the author’s internal representation. Now, if a new formatting requirement arises—say, displaying the author’s details as JSON—you can create a new formatter class without touching the BlogPost or Author classes. This approach embraces the Single Responsibility Principle, one of the core tenets of clean code.

Refactoring with Clean Code Principles

At the heart of refactoring lies the philosophy of clean code, a set of principles that guide developers toward clarity, simplicity, and maintainability. Clean code isn’t just about making things pretty; it’s about making the code easier to read, understand, and extend. A few core principles of clean code shine during refactoring:

Readable Naming Conventions

Naming is one of the hardest parts of coding, and yet it’s one of the most important. Names like doStuff or processmight make sense when you write them, but six months later, they’re as opaque as a foggy morning. During refactoring, take the opportunity to rename variables, functions, and classes to better describe their purpose. For instance:

// Before refactoring
function calc(num, isVIP) {
  if (isVIP) return num * 0.8;
  return num * 0.9;
}

// After refactoring
function calculateDiscount(price, isVIP) {
  const discountRate = isVIP ? 0.2 : 0.1;
  return price * (1 - discountRate);
}

Avoiding Magic Numbers

Numbers like 0.8 or 0.9 might mean something to you now, but they’ll confuse future readers. Extract them into meaningful constants:

const VIP_DISCOUNT = 0.2;
const REGULAR_DISCOUNT = 0.1;

function calculateDiscount(price, isVIP) {
  const discountRate = isVIP ? VIP_DISCOUNT : REGULAR_DISCOUNT;
  return price * (1 - discountRate);
}

Minimizing Conditionals

Nested conditionals are a prime candidate for refactoring. Instead of deep nesting, consider a lookup table:

const discountRates = {
  regular: 0.1,
  vip: 0.2,
};

function calculateDiscount(price, customerType) {
  const discountRate = discountRates[customerType] || 0;
  return price * (1 - discountRate);
}

This approach not only simplifies the code but also makes it easier to add new customer types in the future.

Design Patterns: The Backbone of Robust Refactoring

Refactoring is also an opportunity to introduce design patterns, reusable solutions to common problems that improve the structure and clarity of your code. For example:

In the blog post example, the formatting logic was moved to a dedicated class. But what if you need multiple formatting strategies? Enter the Strategy Pattern:

class JSONFormatter {
  format(author) {
    return JSON.stringify({ name: author.name, bio: author.bio });
  }
}

class TextFormatter {
  format(author) {
    return `${author.name} - ${author.bio}`;
  }
}

// BlogPost remains unchanged

With this pattern, adding a new formatting style is as simple as creating another formatter class.

When creating complex objects, the Factory Pattern can streamline object instantiation. For example, if your BlogPostneeds an appropriate formatter based on the context, a factory can help:

class FormatterFactory {
  static getFormatter(formatType) {
    switch (formatType) {
      case "json":
        return new JSONFormatter();
      case "text":
        return new TextFormatter();
      default:
        throw new Error("Unknown format type");
    }
  }
}

Objectives and Advantages of Refactoring

At its core, refactoring aims to achieve two things:

  • Make the code easier to understand: Clear code leads to fewer bugs and faster development.
  • Make the code easier to extend: Flexible code lets you adapt to new requirements with minimal changes.

The advantages go beyond just clean aesthetics:

  • Reduced technical debt: Refactoring prevents small problems from snowballing into major issues.
  • Improved collaboration: Clean, readable code is easier for teams to work with.
  • Better performance: Streamlined logic often results in faster execution.
  • Future-proofing: Decoupled, modular code is better equipped to handle future changes.

Harnessing the Power of GitHub Copilot for Refactoring: Strategies, Techniques, and Best Practices

Refactoring is a developer’s silent crusade—an endeavor to bring clarity and elegance to code that’s grown unruly over time. And while the craft of refactoring has always been a manual, often meditative process, GitHub Copilot introduces a new ally into the mix. It’s like having a seasoned developer looking over your shoulder, suggesting improvements, and catching things you might miss. But as with any powerful tool, knowing how to wield it effectively is key to maximizing its benefits.

When embarking on a refactoring journey with Copilot, the first step is always understanding your codebase. Before you even type a single keystroke, take a moment to navigate the existing code. What are its pain points? Where does complexity lurk? Identifying these areas is crucial because, like any AI, Copilot is only as good as the questions you ask it.

Let’s say you’re working on a function that calculates the total price of items in a shopping cart:

function calculateTotal(cart) {
  let total = 0;
  for (let i = 0; i < cart.length; i++) {
    if (cart[i].category === "electronics") {
      total += cart[i].price * 0.9;
    } else if (cart[i].category === "clothing") {
      total += cart[i].price * 0.85;
    } else {
      total += cart[i].price;
    }
  }
  return total;
}

This function works, but it’s a bit clunky. Multiple if-else conditions make it hard to add new categories or change existing ones. A great prompt to Copilot would be:

“Refactor this function to use a lookup table for category discounts.”

Copilot might suggest something like this:

const discountRates = {
  electronics: 0.1,
  clothing: 0.15,
};

function calculateTotal(cart) {
  return cart.reduce((total, item) => {
    const discount = discountRates[item.category] || 0;
    return total + item.price * (1 - discount);
  }, 0);
}

With this refactor, the function is now leaner, easier to extend, and more expressive. The original logic is preserved, but the structure is improved—a classic example of effective refactoring.

Techniques for Effective Refactoring with Copilot

Identifying Code Smells with Copilot

One of the underrated features of Copilot is its ability to identify code smells on demand. Ask it directly:

“Are there any code smells in this function?”

Copilot might highlight duplicated logic, overly complex conditionals, or potential performance bottlenecks. It’s like having a pair of fresh eyes every time you revisit your code.

Simplifying Conditionals and Loops

Complex conditionals and nested loops are ripe for refactoring. If you present a nested loop or a deep conditional to Copilot and ask:

“How can I simplify this logic?”

Copilot can suggest converting nested conditionals into a strategy pattern, or refactoring loops into higher-order functions like map, filter, or reduce. The result? Code that is not only more concise but also easier to read and maintain.

For example, converting a nested loop into a more functional approach:

// Before
for (let i = 0; i < orders.length; i++) {
  for (let j = 0; j < orders[i].items.length; j++) {
    console.log(orders[i].items[j].name);
  }
}

// After using Copilot's suggestion
orders.flatMap(order => order.items).forEach(item => console.log(item.name));

Removing Dead Code

Dead code is like that box in your attic labeled “Miscellaneous” — you don’t need it, but it’s still there. By asking Copilot:

“Is there any dead code in this file?”

It can point out unused variables, redundant functions, or logic that never gets executed. Cleaning this up not only reduces the file size but also makes the codebase easier to navigate.

Refactoring Strategies and Best Practices with Copilot

Refactoring isn’t just about changing code; it’s about changing code wisely. Here are some strategies to guide your use of Copilot:

Start Small, Think Big

Begin with minor improvements. Change a variable name, simplify a function, or remove a bit of duplication. Use Copilot to suggest these micro-refactors. Over time, these small changes compound, leading to a more maintainable codebase.

Keep it Testable

Refactoring without tests is like renovating a house without checking the foundation. Before refactoring, ensure you have tests in place. If not, use Copilot to generate basic tests:

“Generate unit tests for this function.”

Once tests are in place, refactor with confidence, knowing that any unintended behavior changes will be caught.

Use Design Patterns When Appropriate

Refactoring often reveals opportunities to introduce design patterns like Singleton, Factory, or Observer. Ask Copilot:

“Refactor this into a Singleton pattern.”

It can scaffold the structure, and you can then refine it to fit your needs. Design patterns not only organize your code better but also make it easier for other developers to understand the architecture at a glance.

Document the Refactor

Every significant refactor deserves a comment or a commit message explaining the change. This isn’t just for others—it’s for you, too, six months down the line when you’re wondering why you made a change. Use Copilot to draft these messages:

“Draft a commit message explaining this refactor.”

The Advantages of Refactoring with Copilot

Efficiency Boost

Refactoring, while necessary, can be time-consuming. Copilot accelerates the process by suggesting improvements and generating boilerplate code.

Learning and Mentorship

Copilot acts as a mentor, introducing you to best practices and modern JavaScript idioms you might not have discovered otherwise. It’s a way to learn by doing, with an intelligent assistant guiding the way.

Improved Code Quality

With Copilot’s help, you can consistently apply clean code principles, reduce technical debt, and enhance the overall quality of your codebase.

Enhanced Collaboration

Refactored code is easier for others to read and extend. A cleaner codebase fosters better collaboration and reduces onboarding time for new team members.

The Journey of Continuous Improvement

Refactoring with GitHub Copilot is a journey, not a destination. Each suggestion, each refactor, and each test is a step toward cleaner, more maintainable code. By integrating clean code principles, embracing design patterns, and leveraging Copilot’s AI-driven insights, you not only improve the current state of your code but also pave the way for a more robust and flexible future.

So, as you embark on your next refactor, invite Copilot to the table. Let it help you think critically about your code, suggest improvements, and enhance your productivity. Because at the end of the day, refactoring isn’t just about code—it’s about crafting a better experience for every developer who walks through the door after you.

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