Creating Temporary Fields in Web Forms

There are a few ways I've seen of displaying field-like inputs on the web without storing them in the submitted document, but I think what I'm about to describe is the easiest way of all.

Basically you don't give the field a name, but give it an ID instead. For example:

<input id="ToDo_tmp" type="text" />

In the browser this looks and acts like a real field. However, when you come to submit the form it isn't counted as a "Successful Control" and its name/value isn't sent to the server.

These kind of fields are really useful sometimes. As a simple example take the ToDo list form from the other week. As I mentioned then, the code added the given value to a set of hidden fields, all with the same name, which can be saved in a multi-value field.

Imagine we had a real field on our form called "ToDo" with "type="\hidden\"" in its HTML Attributes. This field is multi-value and separated by semi-colons. Using a clickable button, JavaScript and our temporary field we can add its values like so:


Or, for you Prototype fans:


Obviously not a great example, but you get the idea, right? To add the temporary field you can use PassThru HTML and you can even give it a value using Computed Text. Note that this applies to all field types. Not just plain text ones.


  1. That's handy. I don't think I've used that particular exploit before. With the prevalence of operating on field id's, however, I wonder how long before some browser decides this is equivalent to a field name. Nice tip though.

    • avatar
    • Jake Howlett
    • Mon 26 Jun 2006 08:35 AM

    Jerry. As I understand it the browser should only submit the field to the server if the name is given. If a browser to send an id/value pair it's breaking the W3C guidelines.

  2. Isn't name a required attribute - meaning that this would cause a page to fail vailidation?

    • avatar
    • Jake Howlett
    • Mon 26 Jun 2006 10:13 AM

    Hi Peter. I just ran this page through the W3C validator and it didn't mention it.

  3. This is an awesome method to allow browser-only fields for UI functionality without cluttering up your document with 30 fields that have a "tmp_" prefix. Good stuff!

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Written by Jake Howlett on Mon 26 Jun 2006

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