How to Update a JSON Field When Another Field Changes in HTML JavaScript?

Learn how to easily update a JSON field in HTML using JavaScript when another field is changed. This guide walks you through step-by-step solution to implement dynamic updates on your web form.
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How to Update a JSON Field When Another Field Changes in HTML JavaScript?

Are you working with forms in HTML and want to automatically update a JSON field when another field's value changes? This can be a common requirement in scenarios where you want to manage a dynamic data structure, especially in modern web applications. Whether you're building a simple form or a more complex user interface, this guide will show you the key steps to achieve this functionality.

The Problem

You have a form with two input fields: one for the brand (let's say it’s a car brand) and another for color. You also have a read-only input field that displays the JSON representation of these two fields. You want the JSON field to automatically update its value whenever either the brand or color is changed.

Example Form Structure

Here’s what your form looks like:

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

The Solution

To implement the functionality you desire, you need to do the following:

Add an onchange event to the input fields: This will trigger an update function whenever the input value changes.

Create a JavaScript function that constructs the JSON object using the values from the brand and color fields and updates the JSON field accordingly.

Step-by-Step Guide

Step 1: Modify the Input Fields

You need to add the onchange event to both input fields. Here’s the updated HTML with the required changes:

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

Step 2: Implement the JavaScript Function

Add the following JavaScript code at the end of your HTML file or in an external JavaScript file. This function will handle the updates to the JSON field:

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

How It Works

onchange Event Listener: Every time the user changes the value of the "brand" or "color" field, the updateJsonField() function is called.

Updating the JSON Field: It constructs a JSON object with those values and updates the read-only json_field with the newly created JSON string using JSON.stringify().

Full Example

Here’s what your final code will look like:

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

Conclusion

Updating a JSON field dynamically as other fields change is a simple yet powerful feature that enhances user experience on web forms. By following these steps, you can easily implement this functionality and create more interactive web applications.

Now you’re equipped to make your forms smarter and more responsive. If you have any questions or need further clarification, feel free to ask!