// 创 建 一 个cookie 
function setCookie(name,value,expires){ 
document.cookie=name+"="+escape(value)+";"+"expires="+expires+";"
} 

// 访 问cookie 
function getCookieVal(offset){ 
var endstr=document.cookie.indexOf(";",offset); 
if (endstr==-1)  endstr=document.cookie.length;
return unescape(document.cookie.substring(offset,endstr));
}

function getCookie(name){
var arg=name+"="; 
var alength=arg.length;
var clength=document.cookie.length; 
var i=0; 
while(i< clength){
var j=i+alength;
if (document.cookie.substring(i,j)==arg)
return getCookieVal(j);
i=document.cookie.indexOf(" ",i)+1; 
if(i==0) break; 
}
return null;
}