function setCookie(name,value)
{
  var Days = 30; //此 cookie 将被保存 30 天
  var exp  = new Date();    //new Date("December 31, 9998");
  exp.setTime(exp.getTime() + Days*24*60*60*1000);
  document.cookie = name + "="+ escape(value) +";expires="+ exp.toGMTString();
}
function getCookie(name)
{
  var arr = document.cookie.match(new RegExp("(^| )"+name+"=([^;]*)(;|$)"));
  if(arr != null) return unescape(arr[2]); return null;
}
function delCookie(name)
{
  var exp = new Date();
  exp.setTime(exp.getTime() - 1);
  var cval=getCookie(name);
  if(cval!=null) document.cookie=name +"="+cval+";expires="+exp.toGMTString();
}


删除所有cookies

function clearCookie(){
var keys=document.cookie.match(/[^ =;]+(?=\=)/g);
if (keys) {
for (var i = keys.length; i--;)
document.cookie=keys[i]+'=0;expires=' + new Date( 0).toUTCString()
}
}