What is the best field validation plugin for Prototype?

Question

Not wanting to re-invent the wheel or anything, I was wondering if there's a plugin out there a field or form validation plugin that works with Prototype that you can recommend from your own experience and why?

Answer 1

I like Ben Keen's Really Simple Validation component.

Features I like:

All the validation rules can be kept within javascript so you're not adding class="required" to your HTML code.

You can display error messages in a javascript alert box or with HTML text.

Adding your own extensions is easy.

http://www.benjaminkeen.com/software/rsv/

Note that I've only used the jQuery version, but a Prototype version is also available.

Answer 2

I like wforms. Example:

<input type="text" name="myDate" class="validate-date"/>

Answer 3

JSValidate