Price updating js from a WordPress theme

gistfile1.js

function checkstock(attval)
{
	var attrs = attval.split(',');
	document.getElementById("cat").value = attrs[0];
	if(eval('document.getElementById("shoppingcart_button_1")'))
	{
		document.getElementById("shoppingcart_button_1").style.display="";
	}
	if(eval('document.getElementById("shoppingcart_outofstock_msg1")'))
	{
		document.getElementById("shoppingcart_outofstock_msg1").innerHTML="";
	}
	if(eval('document.getElementById("shoppingcart_button_2")'))
	{
		document.getElementById("shoppingcart_button_2").style.display="";
	}
	if(eval('document.getElementById("shoppingcart_outofstock_msg2")'))
	{
		document.getElementById("shoppingcart_outofstock_msg2").innerHTML="";
	}
		chkOrder();
}