Only display the loyalty mobile warning once every 2 days (setting a cookie)

gistfile1.js

<!-- Loyalty mobile warning -->
<script>
$(document).ready(function() {      
    var isMobile = window.matchMedia("only screen and (max-width: 760px)");
    var isCookieSet = getCookie('loyalty_mobile_warning');
    if (isMobile.matches && isCookieSet === false) {
    	setCookie('loyalty_mobile_warning', '1', 2);
        alert("The 680 NEWS Insider Club is optimized to work best on a computer or tablet. Please log in using one of those devices. If you are on a smartphone, rotate it to landscape mode.")
    }
 });

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) == 0) return c.substring(name.length,c.length);
    }
    return false;
}

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;
}
</script>