用javascript操作cookie

1，设置cookie（name是自定义的cookie名字标识，value为保存的信息，expires为有效时间，path存放路径，domain存放域名（没怎么用），secure貌似没用到
//set cookie
function set_cookie(name,value,expires,path,domain,secure )
{
// set time, it's in milliseconds
var today = new Date();
today.setTime(today.getTime());
if (expires){
expires = expires * 1000 * 60 * 60 * 24;
}
var expires_date = new Date(today.getTime() + (expires));
document.cookie = name + "=" +escape(value)
+ ((expires)?";expires=" + expires_date.toGMTString() : "" )
+ ((path)?";path=" + path : "")
+ ((domain)?";domain=" + domain : "" )
+ ((secure)?";secure" : "" );
}

2.根据cookie名字标识获取本地的cookie值，怎么取看代码就马上可以看出来了
//get cookie
function get_cookie(name){
var start = document.cookie.indexOf( name + "=" );
var len = start + name.length + 1;
if ((!start)&&(name != document.cookie.substring( 0, name.length )))
{
return null;
}
if ( start == -1 ) return null;
var end = document.cookie.indexOf( ";", len);
if ( end == -1 ) end = document.cookie.length;
return unescape(document.cookie.substring( len, end ));
}

3.删除cookie，虽然叫delete，其实只是把有效日期搞得很久很久以前了而已
function delete_cookie( name, path, domain ) {
if (get_cookie(name))
document.cookie = name + "=" + ((path)?";path=" + path : "")
+ ((domain)?";domain=" + domain : "")
+ ";expires=Thu, 01-Jan-1970 00:00:01 GMT";
}