Скачать или смотреть Understanding DOM Manipulation in JavaScript: Fixing Value Retrieval in Your Calculator Project

Learn how to efficiently retrieve and manipulate DOM values in JavaScript, specifically for building a calculator. This guide will address common pitfalls and provide effective solutions for your first coding project.
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This video is based on the question https://stackoverflow.com/q/63678595/ asked by the user 'dev-vp' ( https://stackoverflow.com/u/14199102/ ) and on the answer https://stackoverflow.com/a/63678671/ provided by the user 'Roko C. Buljan' ( https://stackoverflow.com/u/383904/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding DOM Manipulation in JavaScript: Fixing Value Retrieval in Your Calculator Project

Building a calculator can be an exciting challenge for beginners in JavaScript. However, encountering issues while trying to retrieve values using the Document Object Model (DOM) is a common hurdle. If you're new to JavaScript and find yourself puzzled about why you're unable to get the display value to pass through to your function, this guide is for you.

The Problem: Value Retrieval Issues

In the context of your project, you've created a simple calculator with a display input and buttons for numbers. However, you're struggling to get the display value correctly due to some minor oversight. Here’s a refined look at what you're doing:

Your HTML Structure

Here's the basic HTML structure of your calculator:

[[See Video to Reveal this Text or Code Snippet]]

Your JavaScript Code

And here’s the initial attempt in JavaScript:

[[See Video to Reveal this Text or Code Snippet]]

At first glance, the structure looks correct, but there are a couple of issues causing the malfunction.

The Solution: Correcting the Issues

To resolve your problems with understanding how to get values from the DOM, here are the necessary changes:

1. Use document.forms Instead of document.form

This is a small but crucial change; you need to refer to document.forms (note the plural) to access your form elements correctly.

2. Convert Input Values from String to Numbers

In JavaScript, input values retrieved from forms are always strings. To perform a mathematical operation, it's essential to convert them to a number using parseFloat() or parseInt().

Revised JavaScript Code

Here’s an updated version of your JavaScript function:

[[See Video to Reveal this Text or Code Snippet]]

Improving Your Code Structure

For better practices and cleaner code, consider avoiding inline event handlers. Instead, you can create event listeners, which separate your JavaScript from your HTML for easier debugging and maintenance.

Example of Improved Code Structure

[[See Video to Reveal this Text or Code Snippet]]

Corresponding Improved HTML

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these corrections and best practices, you'll successfully retrieve and manipulate values in your calculator project. Remember that every small adjustment contributes to a more robust and maintainable codebase. With practice, you'll become more comfortable with DOM manipulation and JavaScript functions. Keep coding, and good luck with your calculator project!