cookie的存取删

存：
document.cookie = "name=Kevin;expires="+new Date().getDate()+7; //有效期7天
取：
function GetCookie(sName)
{
var aCookie = document.cookie.split("; ");
for (var i=0; i < aCookie.length; i++)
{
var aCrumb = aCookie[i].split("=");
if (sName == aCrumb[0])
return unescape(aCrumb[1]);
}
return null;
}
GetCookie('name')      //Kevin

//设置cookie  
function setCookie(cname, cvalue, exdays) {  
    var d = new Date();  
    d.setTime(d.getTime() + (exdays*24*60*60*1000));  
    var expires = "expires="+d.toUTCString();  
    document.cookie = cname + "=" + cvalue + "; " + expires;  
}  
//获取cookie  
function getCookie(cname) {  
    var name = cname + "=";  
    var ca = document.cookie.split(';');  
    for(var i=0; i<ca.length; i++) {  
        var c = ca[i];  
        while (c.charAt(0)==' ') c = c.substring(1);  
        if (c.indexOf(name) != -1) return c.substring(name.length, c.length);  
    }  
    return "";  
}  
//清除cookie    
function clearCookie(name) {    
    setCookie(name, "", -1);    
}    
function checkCookie() {  
    var user = getCookie("username");  
    if (user != "") {  
        alert("Welcome again " + user);  
    } else {  
        user = prompt("Please enter your name:", "");  
        if (user != "" && user != null) {  
            setCookie("username", user, 365);  
        }  
    }  
}  
checkCookie();