Skip to content

Split Large Components/Functions Into Smaller Ones

Breaking down large, monolithic components or functions into smaller, manageable pieces is a core principle of writing maintainable code. This approach leads to improved readability, testability, and reusability. Rather than dealing with a single large block of code, smaller units allow for easier understanding, debugging, and future enhancements.

Benefits

  1. Improved Readability: Smaller components or functions are easier to read and understand, as they focus on a specific piece of logic or UI.

  2. Easier Debugging: When something goes wrong, it’s much easier to debug small, isolated pieces of logic than one large function or component.

  3. Better Reusability: Small components and functions can be reused in multiple places, reducing the need to duplicate code.

  4. Simpler Testing: It’s easier to write tests for smaller functions or components that handle one responsibility. Unit testing is much more effective when each test case is focused on one thing.

  5. Enhanced Maintainability: It’s much easier to modify or extend a smaller function or component without breaking unrelated functionality.

Examples

Good Example (Multiple Small Functions)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
function calculateDiscount(price, discount) {
    return price * discount;
}

function calculateTax(price, taxRate) {
    return price * taxRate;
}

function calculateTotal(price, discount, taxRate) {
    const discountedPrice = calculateDiscount(price, discount);
    const tax = calculateTax(discountedPrice, taxRate);
    return discountedPrice + tax;
}

In this example, each function has a single responsibility: calculating discount, tax, and total. This is easy to read and maintain.

Bad Example (One Big Function)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
function calculateTotal(price, discount, taxRate) {
    if (discount > 0) {
        price = price - price * discount;
    }

    if (taxRate > 0) {
        price = price + price * taxRate;
    }

    return price;
}

In this example, the calculateTotal function is doing too much. It handles both the discount and tax logic, making it harder to modify or extend. It’s also difficult to test individual parts of the calculation.

Better Example (React Component)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
function Button({ label, onClick }) {
    return <button onClick={onClick}>{label}</button>;
}

function IconButton({ icon, onClick }) {
    return (
        <button onClick={onClick}>
            <img src={icon} alt="icon" />
        </button>
    );
}

function App() {
    const handleClick = () => console.log('Button clicked!');

    return (
        <div>
            <Button label="Click me" onClick={handleClick} />
            <IconButton icon="path-to-icon.svg" onClick={handleClick} />
        </div>
    );
}

In this React example, the Button and IconButton components each have a specific responsibility: displaying a button with text or an icon. The App component assembles them together. This makes the codebase easier to maintain and extend.

Bad Example (One Big Component)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
function App() {
    const handleClick = () => console.log('Button clicked!');

    return (
        <div>
            <button onClick={handleClick}>Click me</button>
            <button onClick={handleClick}>
                <img src="path-to-icon.svg" alt="icon" />
            </button>
        </div>
    );
}

Here, App directly manages both button types, making it less reusable, harder to test, and harder to modify later (e.g., if you want to change the button style or logic).

Considerations for Complex Components

When a component grows too large or starts handling multiple concerns (such as UI layout and business logic), it's a good sign that you need to break it down further. Identify logical boundaries within the code and refactor parts into smaller, independent components or functions.