Separation of concerns

Separation of concerns is a design principle that encourages developers to separate different parts of a software application into distinct sections. This helps to improve the readability, maintainability, and scalability of the codebase. In this guide, we will discuss the concept of separation of concerns and how it can be applied to web development using JavaScript.

In the previous section, we created a simple JavaScript program that displayed a message in the console. In this section, we will learn how to separate the different concerns of a web application, such as HTML, CSS, and JavaScript, into distinct files.

What are concerns?

In the context of software development, a concern is a specific aspect of a software application that can be separated from other concerns. For example, the user interface, data storage, and business logic are all different concerns of a software application. By separating these concerns into distinct sections, developers can work on each part independently without affecting the other parts.

Why separate concerns?

Separating concerns in a software application has several benefits, including:

Readability: Separating concerns makes the codebase easier to read and understand. Developers can quickly locate and modify specific parts of the code without having to navigate through unrelated sections.
Maintainability: Separating concerns makes it easier to maintain and update the codebase. Changes to one concern do not affect other concerns, reducing the risk of introducing bugs or breaking existing functionality.
Scalability: Separating concerns makes it easier to scale the codebase as the application grows. New features can be added without affecting existing functionality, and the codebase can be refactored or extended more easily.
Reusability: Separating concerns allows developers to reuse code across different parts of the application. Common functionality can be extracted into separate modules or libraries and shared between different concerns.
Collaboration: Separating concerns makes it easier for multiple developers to work on the same codebase. Each developer can focus on a specific concern without interfering with the work of others, improving productivity and reducing conflicts.

Separating concerns in web development

In web development, concerns are typically separated into three main sections: HTML, CSS, and JavaScript. Here's how each concern is used in a web application:

HTML: HTML is used to define the structure and content of a web page. It provides the basic layout of the page, including headings, paragraphs, images, links, and other elements. HTML is a markup language that is used to create the skeleton of a web page.
CSS: CSS is used to define the style and appearance of a web page. It provides the visual design of the page, including colors, fonts, margins, padding, and other styles. CSS is a styling language that is used to create the look and feel of a web page.
JavaScript: JavaScript is used to add interactivity and functionality to a web page. It provides dynamic behavior to the page, including animations, form validation, event handling, and other features. JavaScript is a programming language that is used to create interactive web applications.

Example of separation of concerns

Let's look at an example of how concerns can be separated in a web application. In this example, we will create a simple web page that displays a heading and a button. When the button is clicked, a message will be displayed in the console.

This is a single HTML file that contains all the concerns (HTML, CSS, and JavaScript) in one file:

index.html
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Separation of Concerns</title>
        <style>
            button {
                padding: 10px 20px;
                background-color: #007bff;
                color: #fff;
                border: none;
                cursor: pointer;
            }
        </style>
    </head>
    <body>
        <h1>Welcome to Separation of Concerns</h1>
        <button onclick="console.log('Button clicked')">Click me</button>
        <script>
            console.log('Page loaded');
        </script>
    </body>
</html>

In this example, the HTML, CSS, and JavaScript concerns are all mixed together in a single file. This makes it difficult to read and maintain the code, especially as the application grows in complexity. Even though, the code works perfectly fine, it is not a good practice to mix concerns in a single file.

Separating concerns into distinct files

To separate the concerns into distinct files, we can create separate files for HTML, CSS, and JavaScript. Here's how the earlier code can be refactored into separate files:

We can create an index.html file for the HTML concern:

index.html
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Separation of Concerns</title>
        <link rel="stylesheet" href="styles.css">
    </head>
    <body>
        <h1>Welcome to Separation of Concerns</h1>
        <button id="btn">Click me</button>
        <script src="script.js"></script>
    </body>
</html>

We can create a styles.css file for the CSS concern:

styles.css
button {
    padding: 10px 20px;
    background-color: #007bff;
    color: #fff;
    border: none;
    cursor: pointer;
}

We can create a script.js file for the JavaScript concern:

script.js
document.getElementById('btn').addEventListener('click', function() {
    console.log('Button clicked');
});

By separating the concerns into distinct files, we can improve the readability, maintainability, and scalability of the codebase. Each concern is now contained in a separate file, making it easier to work on each part independently without affecting the other parts.

Conclusion

Separation of concerns is an important design principle that helps developers create more maintainable and scalable software applications. By separating different concerns into distinct sections, developers can improve the readability, maintainability, and scalability of the codebase

In web development, concerns are typically separated into HTML, CSS, and JavaScript, each serving a specific purpose in creating interactive and visually appealing web applications.

Next, we will be talking about JavaScript in Node.js

Made with ❤️ by Fasakin Henry

What are concerns?​

Why separate concerns?​

Separating concerns in web development​

Example of separation of concerns​

Separating concerns into distinct files​

Conclusion​