Building a Mortgage Calculator Web App with Vanilla HTML, CSS, and JavaScript.

This project-based guide shows you how to create a mortgage calculator web app using only HTML, CSS, and JavaScript. Designed for beginners with basic knowledge of these core technologies, the book focuses on writing real, functional code for a practical use case.

Presented in a clear Q&A format, each section covers a step in the development process, including project setup, input validation, mortgage calculations, and displaying results. You’ll also learn how to style your app with CSS, write interactive JavaScript, and test your work in the browser.

You will learn how to:

• Structure a web form for loan inputs
• Perform calculations for monthly payment, interest, and total cost
• Validate user input and display real-time results
• Use CSS for layout, spacing, and responsiveness
• Test and debug using built-in browser tools

By the end of this guide, you’ll have built a complete web app and gained skills you can apply to other front-end projects.