设置cookie

function setCookie(name, value, expiredays) {
    var exdate = new Date()
    exdate.setDate(exdate.getDate() + expiredays)
    document.cookie = name + "=" + escape(value)
            + ((expiredays == null) ? "" : ";expires=" + exdate.toGMTString())
}
function getCookie(name) {
    if (document.cookie.length > 0) {
        var c_start = document.cookie.indexOf(name + "=")
        if (c_start != -1) {
            c_start = c_start + name.length + 1
            var 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 ""
}