---- dataentry snippet ----
type          : snippet # do not change this line
category      : Add to cart form # mention the category like 'shipping', 'checkout' etc
name          : Add To Cart Form Field Validation # the name of the snippet
description   : Validate form fields before adding a product to the cart # description about snippet
versions_tags : 0.7.0, 0.7.1, 0.7.2, 1.0, 1.1 # compatible versions ( always use the dots between the numerals e.g 0.6.0 or 0.7.1 )
reference_url : http://forum.foxycart.com/comments.php?DiscussionID=5246&page=1 # Item_7            # External link
tags_tags     : validation # tags, separated by commas.
date_dt       : 2011-11-18 # the date in YYYY-MM-DD format
----


====== Validating Add-To-Cart Form Inputs ======

Assuming a basic HTML add-to-cart form like this, where you want to ensure that the ''select'' element isn't empty before you all the product to be added to the cart:
<code html>
<form action="https://buckcard.foxycart.com/cart" class="foxycart" name="form6" id="form6" method="post">
    <input type="hidden" name="name" value="Fancy T-Shirt" />
    <input type="hidden" name="price" value="19.95" />

    <strong>Size:</strong>
    <select name="shirt_size" id="shirt_size">
        <option value="small">small</option>
        <option value="medium">medium</option>
        <option value="large">large</option>
    </select>

    <input type="submit" name="submit" value="Buy Now" />
</form>
</code>

You'd use some javascript like this (inside a ''<script>'' tag), changing the ''shirt_size'' as needed:
<code javascript>
custom_validation = function(e, arr) {
    var errors = 0; // Let's set a variable called 'errors', and set the value to 0.

    // This is where you can set the input(s) that you'd like validated
    var shirt_size = jQuery(e).find('select[name="shirt_size"]')[0];

    // Here we'll count the errors, and allso apply an .error class if you want to style the input to alert the user
    if (!jQuery(shirt_size).val()) {
        errors++;
        jQuery(shirt_size).addClass('error');
    }else{
        jQuery(shirt_size).removeClass('error');
    }

    if (errors > 0) {
        alert('Please choose a Widget!');
        return false;
    } else {
        return true;
    }
}
fcc.events.cart.preprocess.add(custom_validation);
</code>