How to make configurable options autoselected on Product view page

If you ever tried to do anything with Magento configurable products view page, most likely you needed changes in  /js/varien/product.js in case you wanted to manipulate dropdowns.

This will be one of the ways to do it.

Basically, what we need to do in order to make initial selection of a product is the following:

Open this file: /app/design/frontend/default/your_theme/template/catalog/product/view/type/options/configurable.phtml

Right below

var spConfig = new Product.Config(< ?php echo $this->getJsonConfig() ?>);

add this JavaScript code:

//we create new function
 
spConfig.setInitialState = function(dropdown_id)
{
 
//select dropdown
 
var dropdown = $(dropdown_id);
//remove empty option from dropdown so it is not selectable after initial selection
 
dropdown[0].remove();
//change selections in dropdowns
for(index = 0; index < dropdown.length; index++)
{
 
if(dropdown[index].value != "")
{
dropdown.selectedIndex = index;
 
var element = dropdown;
var event = 'change';
 
//fire events
if(document.createEventObject)
{
 
var evt = document.createEventObject();
return element.fireEvent('on'+event,evt)
}
else
{
 
var evt = document.createEvent("HTMLEvents");
evt.initEvent(event, true, true );
return !element.dispatchEvent(evt);
}
}
}
 
};
 
<!--?php foreach($_attributes as $_attribute): ?-->
spConfig.setInitialState("attribute< ?php echo $_attribute->getAttributeId() ?>")
< ?php endforeach; ?>

That’s it. I hope you can find this usable, however don’t use it on production site without extensive testing.

As you can see, all prototype functions in Magento (and in general) can be added as new into already existing class.

Same way you could override existing methods in existing classes.

I have coded this feature for the purpose of this article and I’m not claiming that it is production ready. It is only for informative purposes.