truncate product destription

[polbulva]

Hello,
I'm trying to make a product description with a limited number of characters and a "more" link.

I used this:

 

 {if $product->description|strlen > 20} 
<p>{$product->description|truncate:20}</p>
<a href="#" onclick="$('#product->description').show(); $(this).hide(); return false;" class="lnk_more">{l s='More'}</a>
{/if}

 

I would like to see a full description after clicking on "more". Does anyone see a mistake?

 

Thank you, Pavel