You will delve into foundational JavaScript concepts vital for web development. You will learn how to use functions to create an interactive web application that calculates the area of a rectangle based on user-provided values.

1. Understanding HTML structure: Recognize the structure of an HTML file and comprehend how to create an interactive user interface by implementing HTML elements like input fields and buttons.

2. JavaScript variable declaration: Grasp the concept of declaring variables in JavaScript and understand their role in storing data retrieved from user input.

3. Retrieving user input with JavaScript: Learn how to use JavaScript to fetch and process user-provided data entered into input fields within an HTML document.

4. Function implementation and execution: Comprehend the creation and execution of JavaScript functions and their role in executing specific tasks, such as performing calculations and dynamically updating HTML content based on user actions.

1. Setting up the environment: Creating HTML and JavaScript files, initializing the basic HTML structure, input fields, and triggering calculation functionality.

2. Defining variables and functions: Declaring variables for user input storage and crafting a calculateArea() function to process this input. Retrieving user-entered values and computing the area of a rectangle based on these values.

3. Displaying calculated result: Dynamically updating the HTML content with the calculated area. Utilize JavaScript to modify specific elements within the HTML document, providing real-time feedback to the user.