function updateQuantity()
{
	var quantity_field = $('#quantity');
	if (isNaN(parseInt(quantity_field.attr('value'))))
		quantity_field.attr('value', '1');
	
	updateTotalPrice();
}

function updateTotalPrice()
{
	var quantity = parseInt($('#quantity').attr('value'));
	var price = parseFloat($('#item_price').attr('value'));
	var total_price = (quantity * price).toString();
	var decimal_place_index = total_price.indexOf('.');
	if (decimal_place_index == -1)
		total_price += '.00';
	$('#price').html('$' + total_price);
}

function addToCart()
{
	var amplifier_id = $('#item_amplifier_id').attr('value');
	var quantity = $('#quantity').attr('value');
	var colour = $('#colour').attr('value');
	var size = $('#size').attr('value');
	
	var url = 'http://ffd.amplifier.co.nz/addtobasket.do?id=' + amplifier_id +
		'&custName' + amplifier_id + '=SIZE&custValue' + amplifier_id + '=' + size + 
		'&custName' + amplifier_id + '=COLOUR&custValue' + amplifier_id + '=' + colour +
		'&quantity=' + quantity;
	var width = 480;
 	var height = 780;
	
	var features = 'scrollbars = yes,resizable = yes,status = no,location = no,toolbar = no,';
	features = features + 'width = '+ width +',height = ' + height;
	window.open(url, 'purchase', features);
}