JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <select name="foo" id="foo" >
        <option value="5" selected="selected">5</option>
        <option value="15">15</option>
        <option value="25">25</option>
    </select>
    <input type="text" name="moo" id="moo" />
    <input type="checkbox" name="boo" id="boo" />
    <input type="radio" name="doo" value="false" />
    <input type="radio" name="doo" value="true" />
    <br/>
    Type test in the textbox and check the checkbox to enable the select.
    <br/>
    By <a href="http://www.balupton.com" target="_blank">Benjamin "balupton" Lupton</a>, for <a href="http://stackoverflow.com/q/3731586/130638" target="_blank">a StackOverflow Question</a>
</div>

CSS

:disabled {
    opacity:0.5;
}
.disabled {
    opacity:0.5;
}

JavaScript

(function($){
    /**
     * jQuery.fn.dependsOn
     * @version 1.0.1
     * @date September 22, 2010
     * @since 1.0.0, September 19, 2010
     * @package jquery-sparkle {@link http://www.balupton/projects/jquery-sparkle}
     * @author Benjamin "balupton" Lupton {@link http://www.balupton.com}
     * @copyright (c) 2010 Benjamin Arthur Lupton {@link http://www.balupton.com}
     * @license Attribution-ShareAlike 2.5 Generic {@link http://creativecommons.org/licenses/by-sa/2.5/
     */
    $.fn.dependsOn = function(source,value){
        var $target = $(this),
            $source = $(source),
            source = $source.attr('name')||$source.attr('id');

        // Add Data
        var dependsOnStatus = $target.data('dependsOnStatus')||{};
        dependsOnStatus[source] = false;
        $target.data('dependsOnStatus',dependsOnStatus);

        // Add Event
        $source.change(function(){
            var pass = false;
            var $source = $(this); // so $source won't be a group for radios

            // Determine
            if ( (value === null) || (typeof value === 'undefined') ) {
                // We don't have a value
                if ( $source.is(':checkbox,:radio') ) {
                    pass = $source.is(':selected:enabled,:checked:enabled');
                }
                else {
                    pass = Boolean($source.val());
                }
            }
            else {
                // We do have a value
                if ( $source.is(':checkbox,:radio') ) {
                    pass = $source.is(':selected:enabled,:checked:enabled') && ($source.val() == value);
                }
                else {
                    pass = $source.val() == value;
                }
            }

            // Update
            var dependsOnStatus = $target.data('dependsOnStatus')||{};
            dependsOnStatus[source] = pass;
            $target.data('dependsOnStatus',dependsOnStatus);

            // Determine
            var...