js使用cookie

//创建cookie
function addCookie(){
var Days = 30;
var exp = new Date();
exp.setTime(exp.getTime() + Days*24*60*60*1000);
document.cookie = "lastUserName" + "="+ escape (un) + ";expires=" + exp.toGMTString();
}
//读取cookie
function getCookie(name) {
var arr,reg=new RegExp("(^| )"+name+"=([^;]*)(;|$)");
if(arr=document.cookie.match(reg))
return unescape(arr[2]);
else
return null;
}
//删除cookies
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();
}else{
document.getElementById("j_username").value="请输入用户名";
}
}