//hours为空字符串时,cookie的生存期至浏览器会话结束。hours为数字0时,建立的是一个失效的cookie,这个cookie会覆盖已经建立过的同名、同path的cookie（如果这个cookie存在）。

function setCookie(name,value,hours,path){

    var name = escape(name);

    var value = escape(value);

    var expires = new Date();

    expires.setTime(expires.getTime() + hours*3600000*3600);

    path = path == "" ? "" : ";path=" + path;

    _expires = (typeof hours) == "string" ? "" : ";expires=" + expires.toUTCString();

    document.cookie = name + "=" + value + _expires + path;

}//新建cookie

function getCookieValue(name){

    var name = escape(name);

    var allcookies = document.cookie;

    name += "=";

    var pos = allcookies.indexOf(name);

    if (pos != -1){

        var start = pos + name.length;

        var end = allcookies.indexOf(";",start);

        if (end == -1) end = allcookies.length;

        var value = allcookies.substring(start,end);

        return unescape(value);

    }

    else return "";

}//获取cookie值

function deleteCookie(name,path){

    var name = escape(name);

    var expires = new Date(0);

    path = path == "" ? "" : ";path=" + path;

    document.cookie = name + "="+ ";expires=" + expires.toUTCString() + path;

}//删除cookie