I am working on a web form that includes a dropdown menu, and I want to add extra input fields that only appear when a certain option is selected from that menu.
Currently, my form looks like this:
<form method="POST" name="emails" action="../emailing.php">
<select size="1" id="email_template" name="email_template_id">
<option value="1">Welcome</option>
<option value="2">Newsletter</option>
<option value="3">Invoice</option>
</select>
<input type="hidden" name="email_template" value="1">
<input type="hidden" name="saleid" value="318">
<input type="hidden" name="usertype" value="admin">
<input type="image" name="emails" id="imageField" src="/images/submit.gif" class="send">
</form>
I would like additional input fields to show up only when the “Invoice” option is selected. These could be one or two input fields, along with a textarea for entering some additional information. It’s important that these fields are included in the form submission.
To achieve the desired functionality, consider implementing event listeners on your dropdown element that can show or hide extra input fields based on the selected option. Initially, create the input fields for additional information wrapped in a div with a style of ‘display:none’. Then, use JavaScript to listen for changes on the dropdown; when the ‘Invoice’ option is selected (value = ‘3’), set the display of the div to ‘block’. This approach ensures that the extra fields are properly included in the form submission only when they are visible.
Dynamic field creation beats toggling visibility for complex forms. Skip hiding divs - use createElement and appendChild to build fields when someone picks Invoice. Keeps your HTML clean and stops unnecessary form data from hitting your server. When the dropdown changes, use removeChild to clear existing fields before creating new ones. I’ve found this works great when different options need totally different field sets. Just store references to your created elements so you can clean them up properly. One thing - dynamically created fields need explicit name attributes or they won’t submit with your form data.
Yeah, standard JavaScript works but you’ll be manually coding every dynamic form.
I’ve done this across dozens of projects. Building conditional form logic from scratch gets messy fast - tons of event handlers, DOM manipulation, and debugging display issues.
Automation saved me countless hours. Instead of custom JavaScript for each form, I set up automated workflows that handle dynamic generation based on user selections.
The workflow listens for dropdown changes, auto-generates required fields, and handles validation. Someone selects “Invoice”? It instantly creates additional fields with proper validation.
This scales beautifully. Need it on other forms? Same automation pattern works everywhere. No more copying JavaScript snippets or debugging DOM issues.
I’ve used this for simple contact forms to complex multi-step wizards. Time savings are incredible, especially when modifying logic later.
Latenode makes this form automation really straightforward. Set up conditional logic visually and deploy immediately: https://latenode.com
I’ve done this in several projects - addEventListener with change events works great. Just create your extra fields in HTML and wrap them in a div with style="display:none". Then use JavaScript to check the selected value. When it hits “3” for Invoice, show the container with style.display = "block", otherwise hide it. Make sure your fields have proper name attributes so they submit when visible. I usually add a quick validation check before submission to confirm required fields are filled when their trigger option is selected. Works consistently across browsers and doesn’t need any external libraries.
use the onchange event right in your select tag. create a hidden div for the invoice fields, then toggle it when the dropdown changes. try document.getElementById('invoiceFields').style.display = selectedValue == '3' ? 'block' : 'none'. no extra libraries needed and it’s dead simple.