function setCookie(name,value,days) {
    var expires = "";
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days*24*60*60*1000));
        expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "")  + expires + "; path=/";
}
function getCookie(name) {
    var nameEQ = name + "=";
    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,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
}

setCookie("user_email","bobthegreat@gmail.com",30); //set "user_email" cookie, expires in 30 days
var userEmail=getCookie("user_email");//"bobthegreat@gmail.com"

function setCookie(name,value,days) {
    var expires = "";
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days*24*60*60*1000));
        expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "")  + expires + "; path=/";
}
function getCookie(name) {
    var nameEQ = name + "=";
    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,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
}
function eraseCookie(name) {   
    document.cookie = name +'=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;';
}

<script type="text/javascript">
    function setCookie(key, value, expiry) {
        var expires = new Date();
        expires.setTime(expires.getTime() + (expiry * 24 * 60 * 60 * 1000));
        document.cookie = key + '=' + value + ';expires=' + expires.toUTCString();
    }

    function getCookie(key) {
        var keyValue = document.cookie.match('(^|;) ?' + key + '=([^;]*)(;|$)');
        return keyValue ? keyValue[2] : null;
    }

    function eraseCookie(key) {
        var keyValue = getCookie(key);
        setCookie(key, keyValue, '-1');
    }

</script>