Code Refactoring: Strategies for Improving Your Existing Codebase

In the fast-paced world of JavaScript development, maintaining a clean and efficient codebase is imperative for sustainable software projects. Code refactoring, the process of restructuring existing code without altering its external behavior, is a critical practice that empowers developers to enhance code readability, maintainability, and performance. In this exploration of code refactoring strategies, we will delve into practical JavaScript examples, demonstrating each technique’s impact on improving your existing codebase.

1. Extract Method:

Original Code:

function calculateTotalPrice(quantity, price) {
    const taxRate = 0.1;
    const discountRate = 0.05;

    let total = quantity * price;
    total = total + (total * taxRate);
    total = total - (total * discountRate);

    return total;
}

Refactored Code:

function calculateTotalPrice(quantity, price) {
    const taxRate = 0.1;
    const discountRate = 0.05;

    let subtotal = quantity * price;
    let total = applyTax(subtotal, taxRate);
    total = applyDiscount(total, discountRate);

    return total;
}

function applyTax(amount, taxRate) {
    return amount + (amount * taxRate);
}

function applyDiscount(amount, discountRate) {
    return amount - (amount * discountRate);
}

Explanation:

• The calculateTotalPrice function has been refactored by extracting the tax and discount calculations into separate methods (applyTax and applyDiscount).
• This enhances readability, promotes code reuse, and makes each function more focused on a specific task.

2. Replace Magic Numbers with Constants:

Original Code:

function calculateArea(radius) {
    return 3.14 * radius * radius;
}

Refactored Code:

const PI = 3.14;

function calculateArea(radius) {
    return PI * radius * radius;
}

Explanation:

• Magic numbers, like 3.14, can be unclear. Replacing them with named constants, like PI, improves code readability and maintainability.
• Constants are defined at the beginning of the script or in a dedicated configuration file for easy modification.

3. Merge Conditional Statements:

Original Code:

function checkCustomerEligibility(age, income) {
    if (age >= 18) {
        if (income > 30000) {
            return "Customer is eligible.";
        }
    }
    return "Customer is not eligible.";
}

Refactored Code:

function checkCustomerEligibility(age, income) {
    if (age >= 18 && income > 30000) {
        return "Customer is eligible.";
    }
    return "Customer is not eligible.";
}

Explanation:

• Merging nested if statements into a single conditional statement simplifies the logic and reduces indentation levels.
• This refactoring makes the code more concise without sacrificing readability.

4. Replace Loops with List Comprehensions:

Original Code:

let squares = [];
for (let num = 1; num <= 5; num++) {
    squares.push(num * num);
}

Refactored Code:

const squares = Array.from({ length: 5 }, (_, index) => (index + 1) ** 2);

Explanation:

• List comprehensions provide a concise and readable way to create lists.
• The refactored code is more idiomatic and expresses the intent of creating a list of squares more directly.

5. Introduce Meaningful Variable Names:

Original Code:

function calculateTriangleArea(b, h) {
    const a = 0.5 * b * h;
    return a;
}

Refactored Code:

function calculateTriangleArea(base, height) {
    const area = 0.5 * base * height;
    return area;
}

Explanation:

• Meaningful variable names make the code self-explanatory and enhance readability.
• The refactored code uses descriptive names (base and height) instead of single-letter variables.

Incorporating these code refactoring strategies into your JavaScript development process can lead to a more maintainable, readable, and robust codebase. Remember that code refactoring is an ongoing practice, and each improvement contributes to the overall health of your software project.