js 实现获取cookie

function getCookie(c_name)
{
if(document.cookie.length>0){
c_start=document.cookie.indexOf(c_name + "=");
if(c_start!=-1){
c_start=c_start + c_name.length+1 ;
c_end=document.cookie.indexOf(";",c_start);
if(c_end==-1) {
c_end=document.cookie.length;
}
return unescape(document.cookie.substring(c_start,c_end));
}
}
return "";
}

//写cookies
function setCookie(name,value)
{
var Days = 30;
var exp = new Date();
exp.setTime(exp.getTime() + Days*24*60*60*1000);
document.cookie = name + "="+ escape (value) + ";expires=" + exp.toGMTString();
}

//读取cookies
function getCookie(name)
{
var arr,reg=new RegExp("(^| )"+name+"=([^;]*)(;|$)");

if(arr=document.cookie.match(reg))

return unescape(arr[2]);
else
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();
}