cookie添加删除修改

//cookie添加
document.cookie="username=John Doe";
//添加过期时间
document.cookie="username1=John Doe1; expires=Thu, 18 Dec 2013 12:00:00 GMT";
//用 path 参数告诉浏览器 cookie 的路径。默认情况下，cookie 属于当前页面。
document.cookie="username2=John Doe2; expires=Thu, 18 Dec 2013 12:00:00 GMT; path=/";
//读取 Cookie
var x = document.cookie;
console.log(x);
//修改 Cookie 也是创建新的覆盖旧的 //删除 Cookie 把期限设置成以前的时间
document.cookie = "username=; expires=Thu, 01 Jan 1970 00:00:00 GMT";
//设置 cookie 值的函数 该函数设置了 cookie 名、cookie 值、cookie过期时间。
function setCookie(cname,cvalue,exdays)
{
var d = new Date();
d.setTime(d.getTime()+(exdays*24*60*60*1000));
var expires = "expires="+d.toGMTString();
document.cookie = cname + "=" + cvalue + "; " + expires;
}
//获取 cookie 值的函数
function getCookie(cname)
{
var name = cname + "=";
var ca = document.cookie.split(';');
for(var i=0; i<ca.length; i++)
{
var c = ca[i].trim();
if (c.indexOf(name)==0) return c.substring(name.length,c.length);
}
return "";
} //检测 cookie 值的函数
function checkCookie()
{
var username=getCookie("username");
if (username!="")
{
alert("Welcome again " + username);
}
else
{
username = prompt("Please enter your name:","");
if (username!="" && username!=null)
{
setCookie("username",username,365);
}
}
}