Local storage

if (localStorage.getItem("cookieAccept") === null) {
    localStorage.setItem("cookieAccept","true");
}

Cookies

var date = new Date();
var days = 100;
date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
var expires = date.toGMTString();
document.cookie = 'accept_cookie=1; expires=' + expires + '; path=/';