function trapEvent(object,tevent,tfunction){if(document.getElementById(object)!==null){eval("document.getElementById(object)."+tevent+"=function(e){"+tfunction+"return false;};");}}
function swapImage(img){var main = document.getElementById('main-image');var thumb = document.getElementById(img);var url_thumb = main.src.substring(0, (main.src.length -4)) + '_thumb.jpg';var alt_thumb = main.alt;var url_big = thumb.src.substring(0, (thumb.src.length -10)) + '.jpg';var alt_big = thumb.alt;main.src = url_big;main.alt = alt_big;thumb.src = url_thumb;thumb.alt = alt_thumb;}
function createSwap(e){var previews = document.getElementById('previews');var thumbs = previews.getElementsByTagName('img');for(var i = 0; i < thumbs.length; i++)	{trapEvent(thumbs[i].id, 'onmouseover', 'swapImage(\''+thumbs[i].id+'\');');}}
window.onload = createSwap;