Скачать или смотреть Updating Input Values with onchange Events in Vanilla JavaScript: A Step-By-Step Guide

Learn how to properly update input values and retrieve them with `onchange` events in vanilla JavaScript for your API calls.
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Updating Input Values with onchange Events in Vanilla JavaScript: A Step-By-Step Guide

When working on web projects that require user input, it's crucial to ensure that you can effectively update and retrieve values when users interact with form fields. In this guide, we will address a common issue faced by many developers, especially beginners: how to update the input value using an onchange event and retrieve that value using vanilla JavaScript.

The Problem

A new developer faced a challenge while working on an assignment that involved making a simple API call to retrieve images of dogs by breed. The user reported that the input value for the breed of dog seemed to revert back to the default value ('hound') after submitting the form, even though they had selected a different breed.

Upon closer inspection, it was clear that the input value had to be dynamically updated before making the API call. The developer initially thought they needed to implement an onchange event for their input field but weren't sure how to proceed.

Understanding the Solution

Why onchange is Not Necessary

The good news is that you don't actually need an onchange event handler in this case. The primary issue stems from how the breedName variable was being defined and used. When the developer first set the breedName, they stored the value at that moment. Hence, it never changed with new user input.

Correct Approach

The correct approach is to create a reference to the input element and read its value inside the event handler when the form is submitted. This ensures that you get the current value of the input field at the time of submission.

Step-by-Step Implementation

HTML Structure: Ensure that your HTML has the correct structure for the form and input fields.

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

JavaScript Functionality: Move the logic to retrieve the input value into the submit event handler.

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

Key Points to Remember

Dynamic Input Value: Always fetch the input value inside the event handler to ensure it reflects the most recent input.

Prevent Default Submission: Using event.preventDefault() stops the form from being submitted the traditional way, allowing you to handle the input dynamically.

Simple and Clean Code: Keeping your JavaScript organized not only improves readability but also makes debugging easier.

Conclusion

Updating input values and retrieving them at the right time is a fundamental concept in web development. With the approach outlined above, you should be able to avoid issues with stale input values and create more interactive applications. Remember, always reference the input field directly to get the latest data!

Feel free to reach out if you have any questions or need further clarification on this topic!