Скачать или смотреть How to Validate Form Inputs with Dynamic Color Changes in JavaScript

Learn how to enhance your form validation with dynamic color changes for empty fields using JavaScript. This guide will teach you how to implement effective input validation on form submission and during user input.
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This video is based on the question https://stackoverflow.com/q/64011773/ asked by the user 'DeveloperLV' ( https://stackoverflow.com/u/12129150/ ) and on the answer https://stackoverflow.com/a/64011951/ provided by the user 'Pranav Rustagi' ( https://stackoverflow.com/u/14046126/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Validate Form Inputs with Dynamic Color Changes in JavaScript

Validating forms is an important aspect of web development. It ensures that the data entered by users is complete and correct before it's submitted. A common requirement is to provide immediate feedback on invalid input fields. One engaging method of achieving this is to change the background color of input fields based on whether they are empty or filled. In this guide, we will explore how to implement this technique using a simple JavaScript solution.

Current Situation

You might already have a basic event listener set up that triggers when the form is submitted. This listener checks if any of the input fields are empty. If an empty field is found, it changes the background color to red and displays a placeholder indicating that the field is required.

Here’s a quick look at what that code might look like:

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

Goal

The goal is to not only check for empty fields on submission but also to allow users to rectify their mistakes. Specifically, if an input turns red due to being empty, it should revert to white once the user starts typing into that field.

Solution Overview

To achieve this, we will:

Add an event listener to the form for the submit event to check for empty fields.

Implement a validation function that not only checks the input on submission but also adds another listener for changes (input events) to each field after the first submission.

Let’s break down the implementation step by step.

Step 1: Setup Form Submission Listener

Start by modifying the existing submission listener. When the form is submitted, prevent the default action to control how validation and submission work:

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

Step 2: Validate Each Input

Within the event listener, loop through each input element and call the validation function:

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

Step 3: Define the Validation Function

Create a validate function that checks if the input is empty and applies styling accordingly:

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

Step 4: Add Input Event Listeners

To allow for real-time feedback, we need to dynamically attach event listeners to each input field for input changes. This should happen only after the form is first submitted.

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

Complete Code

Here’s what the final code will look like:

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

Conclusion

With this approach, users receive immediate visual feedback if they attempt to submit an empty form field, and they can interactively change the input without needing to resubmit the form multiple times. This method not only enhances user experience but also improves the effectiveness of your form validations. By incorporating dynamic color changes with JavaScript, you can create more engaging and user-friendly web forms.

Now that you have the fundamentals of form validation and styling, feel free to customize the colors and styles to better fit the aesthetic of your web application.

Happy coding!