Computer Science Basics Course (CS101) – Module 7
Module 7: Web Development Basics
- Introduction to web technologies (HTML, CSS, JavaScript)
Introduction:
Web technologies form the foundation of modern web development, enabling the creation of interactive and visually appealing websites and web applications. In this lesson, we will introduce the key technologies used in web development, namely HTML (HyperText Markup Language), CSS (Cascading Style Sheets), and JavaScript. These technologies work together to define the structure, style, and behavior of web pages.
- HTML (HyperText Markup Language):
Purpose: HTML is the standard markup language used to create the structure and content of web pages.
Functionality:
Defines the elements and components of a web page, such as headings, paragraphs, images, links, and forms.
Utilizes a tag-based syntax, where elements are enclosed within opening and closing tags (e.g., <p> for paragraphs).
Supports attributes to provide additional information about elements (e.g., src attribute for image sources).
Example:
html
<!DOCTYPE html>
<html>
<head>
<title>My First Web Page</title>
</head>
<body>
<h1>Welcome to My Website</h1>
<p>This is a paragraph of text.</p>
<img src=”example.jpg” alt=”Example Image”>
<a href=”https://example.com”>Visit Example Website</a>
</body>
</html>
- CSS (Cascading Style Sheets):
Purpose: CSS is a style sheet language used to define the presentation and layout of HTML documents.
Functionality:
Allows for the styling of HTML elements, including properties such as color, font, size, margin, padding, and positioning.
Utilizes selectors to target specific HTML elements and apply styling rules.
Supports various units of measurement for specifying sizes and distances, such as pixels, percentages, and ems.
Example:
css
/* CSS Stylesheet */
body {
font-family: Arial, sans-serif;
background-color: #f0f0f0;
}
h1 {
color: blue;
text-align: center;
}
p {
font-size: 16px;
line-height: 1.5;
}
- JavaScript:
Purpose: JavaScript is a scripting language used to add interactivity and dynamic behavior to web pages.
Functionality:
Allows for the manipulation of HTML elements, including adding, removing, or modifying elements and their attributes.
Enables the handling of user interactions, such as mouse clicks, keyboard input, and form submissions.
Supports the creation of animations, transitions, and effects to enhance the user experience.
Example:
javascript
// JavaScript Code
document.getElementById(“myButton”).addEventListener(“click”, function() {
alert(“Button clicked!”);
});
- Integration and Interaction:
Integration: HTML, CSS, and JavaScript work together to create fully functional web pages and applications. HTML provides the structure, CSS adds styling and layout, and JavaScript adds interactivity and dynamic behavior.
Interaction: JavaScript can interact with both HTML and CSS, allowing for dynamic updates to the content, style, and behavior of web pages in response to user actions or other events.
- Practice Exercise:
Problem: Create a simple web page that displays a welcome message and changes its background color when a button is clicked.
Solution:
html
<!DOCTYPE html>
<html>
<head>
<title>Simple Web Page</title>
<style>
body {
font-family: Arial, sans-serif;
background-color: #f0f0f0;
text-align: center;
}
button {
padding: 10px 20px;
background-color: blue;
color: white;
border: none;
cursor: pointer;
}
</style>
</head>
<body>
<h1>Welcome to My Website</h1>
<p>Click the button to change the background color.</p>
<button id=”changeColorButton”>Change Color</button>
<script>
document.getElementById(“changeColorButton”).addEventListener(“click”, function() {
document.body.style.backgroundColor = “lightblue”;
});
</script>
</body>
</html>
- Building a simple web application (front-end and back-end integration)
Objective:
At the end of this lesson, students will be able to:
Understand the architecture of a simple web application with front-end and back-end components.
Implement front-end and back-end functionalities using HTML, CSS, JavaScript (for the front-end) and Node.js (for the back-end).
Integrate front-end and back-end components to create a fully functional web application.
Introduction:
A web application typically consists of two main components: the front-end, which is responsible for the user interface and interactions, and the back-end, which handles data processing, storage, and business logic. In this lesson, we will explore how to build a simple web application by integrating front-end and back-end components using HTML, CSS, JavaScript for the front-end, and Node.js for the back-end.
- Front-End Development:
HTML: Define the structure and content of web pages.
CSS: Style the appearance and layout of web pages.
JavaScript: Add interactivity and dynamic behavior to web pages.
- Back-End Development:
Node.js: A JavaScript runtime environment that allows you to run JavaScript code on the server-side.
Express.js: A web application framework for Node.js that simplifies the process of building back-end APIs and handling HTTP requests.
- Building the Front-End:
HTML Structure: Define the HTML structure of the web pages using tags like <html>, <head>, <body>, and various elements such as <div>, <p>, <form>, etc.
CSS Styling: Apply CSS styles to elements to control their appearance, including properties like color, font, margin, padding, and positioning.
JavaScript Interactivity: Use JavaScript to add interactivity to the web pages, such as handling user input, performing client-side validation, and updating the page content dynamically.
- Building the Back-End:
Setting up Express.js: Install Express.js using npm and set up the basic structure of the server-side application.
Creating Routes: Define routes to handle different HTTP requests (GET, POST, PUT, DELETE) for various resources and functionalities.
Handling Requests: Implement logic to process incoming requests, perform data manipulation or retrieval, and generate appropriate responses.
Connecting to a Database: Integrate with a database (e.g., MongoDB, MySQL) to store and retrieve data as required by the application.
- Integrating Front-End and Back-End:
API Endpoints: Define API endpoints on the back-end to expose functionalities and data to the front-end.
HTTP Requests: Use JavaScript on the front-end to send HTTP requests (e.g., using Fetch API or Axios) to the back-end API endpoints.
Data Exchange: Send data from the front-end to the back-end (e.g., form submissions, user input) and receive responses containing data or status updates.
- Example Project: To-Do List Application:
Front-End: Create a simple to-do list interface using HTML, CSS, and JavaScript to allow users to add, edit, delete, and mark tasks as completed.
Back-End: Implement back-end functionality using Node.js and Express.js to handle CRUD operations (Create, Read, Update, Delete) for managing tasks.
Integration: Connect the front-end to the back-end by sending HTTP requests to the appropriate API endpoints to perform CRUD operations on tasks.
- Practice Exercise:
Problem: Extend the to-do list application to allow users to categorize tasks into different lists (e.g., work, personal) and switch between lists.
Solution: Modify the front-end interface to include a dropdown menu for selecting lists and update the back-end to support multiple lists for tasks.
- Interacting with databases through web applications
Objective:
Introduction: Web applications often need to interact with databases to store and retrieve data dynamically. This interaction involves performing CRUD operations (Create, Read, Update, Delete) on the database to manage data effectively. In this lesson, we will explore how web applications can interact with databases and implement CRUD operations using various technologies.
- Establishing Database Connections:
Connection String: Provide the necessary connection information, such as the database server address, port, username, password, and database name.
Database Driver: Use a database driver or client library compatible with the chosen database management system (e.g., MySQL, PostgreSQL, MongoDB) to establish a connection.
- Performing CRUD Operations:
Create (Insert): Add new records or data entries to the database.
Read (Select): Retrieve data from the database based on specified criteria.
Update: Modify existing data records in the database.
Delete: Remove data records from the database.
- Implementing CRUD Operations in Web Applications:
Front-End Integration: Design user interfaces (UI) to capture user input and display data retrieved from the database.
Back-End Logic: Develop server-side logic to handle HTTP requests from the front-end, validate user input, and perform CRUD operations on the database.
Database Queries: Use SQL (Structured Query Language) or ORM (Object-Relational Mapping) libraries to execute database queries and manipulate data.
- Security Considerations:
Parameterized Queries: Use parameterized queries or prepared statements to prevent SQL injection attacks and ensure data sanitization.
Input Validation: Validate user input on the server-side to prevent malicious or invalid data from being inserted into the database.
Authentication and Authorization: Implement user authentication and authorization mechanisms to control access to sensitive database operations and data.
- Efficiency and Performance:
Indexing: Create indexes on columns frequently used in search and filter operations to improve query performance.
Optimized Queries: Write optimized SQL queries to minimize database load and reduce query execution time.
Connection Pooling: Use connection pooling to manage database connections efficiently and avoid connection overhead.
- Error Handling and Logging:
Error Handling: Implement error handling mechanisms to gracefully handle database errors and exceptions, such as connection failures or query errors.
Logging: Log database interactions, queries, and errors for troubleshooting, auditing, and monitoring purposes.
- Example Project: Blogging Platform:
Front-End: Develop a web interface for users to create, view, update, and delete blog posts.
Back-End: Implement server-side logic using a web framework (e.g., Express.js for Node.js) to handle HTTP requests and perform CRUD operations on the database.
Database Integration: Use SQL or ORM libraries (e.g., Sequelize for Node.js) to interact with the database, execute queries, and manipulate blog post data.
- Practice Exercise:
Problem: Extend the blogging platform to allow users to comment on blog posts. Implement CRUD operations for managing comments in the database and integrate comment functionality into the web application.
Solution: Modify the database schema to include a “comments” table, implement CRUD operations for comments, and update the web application UI and back-end logic to support comment functionality.