function getCookie(c_name) {
    if (document.cookie.length > 0) {
        c_start = document.cookie.indexOf(c_name + "=");
        if (c_start != -1) {
            c_start = c_start + c_name.length + 1;
            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 ""
}

function setCookie(c_name, value, expiredays) {
    var exdate = new Date();
    exdate.setDate(exdate.getDate() + expiredays);
    document.cookie = c_name + "=" + escape(value) + ((expiredays == null) ? "" : "; expires=" + exdate.toGMTString());
}

function checkCookie() {
    username = getCookie('username');
    if (username != null && username != "") {
        alert('Welcome again ' + username + '!');
    }
    else {
        username = prompt('Please enter your name:', "");
        if (username != null && username != "") {
            setCookie('username', username, 365);
        }
    }
}