// JavaScript Document
var xmlHttp = false; 
try { 
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); 
} catch (e) { 
try { 
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); 
} catch (e2) { 
xmlHttp = false; 
} 
} 
if (!xmlHttp && typeof XMLHttpRequest != 'undefined') { 
xmlHttp = new XMLHttpRequest(); 
} 
var listid,num;
function callserver(id) { 
listid = id;
num = document.getElementById(id).value;
if (num == null || num == "")return;
if (isNaN(num)){
alert("请输入有效数字");
return;
}
var url = "cart_change_num.php?listid=" + escape(listid) + "&num=" + escape(num) ;
xmlHttp.open("GET", url, true); 
xmlHttp.onreadystatechange = updatePage; 
xmlHttp.send(null); 
} 
function updatePage() {  
if (xmlHttp.readyState == 4) {
var response=xmlHttp.responseText;
   if (response=="1"){
  window.location.href="cart.php";
   return false;
  }else{
  alert("库存不足");
   return false;
  }
}
}