Usare i cookies (da: https://developer.mozilla.org/en/DOM/document.cookie)…:

codice:
docCookies = {
  getItem: function (sKey) {
    if (!sKey || !this.hasItem(sKey)) { return null; }
    return unescape(document.cookie.replace(new RegExp("(?:^|.*;\\s*)" + escape(sKey).replace(/[\-\.\+\*]/g, "\\$&") + "\\s*\\=\\s*((?:[^;](?!;))*[^;]?).*"), "$1"));
  },
  /**
  * docCookies.setItem(sKey, sValue, vEnd, sPath, sDomain, bSecure)
  *
  * @argument sKey (String): the name of the cookie;
  * @argument sValue (String): the value of the cookie;
  * @optional argument vEnd (Number, String, Date Object or null): the max-age in seconds (e.g., 31536e3 for a year) or the
  *  expires date in GMTString format or in Date Object format; if not specified it will expire at the end of session; 
  * @optional argument sPath (String or null): e.g., "/", "/mydir"; if not specified, defaults to the current path of the current document location;
  * @optional argument sDomain (String or null): e.g., "example.com", ".example.com" (includes all subdomains) or "subdomain.example.com"; if not
  * specified, defaults to the host portion of the current document location;
  * @optional argument bSecure (Boolean or null): cookie will be transmitted only over secure protocol as https;
  * @return undefined;
  **/
  setItem: function (sKey, sValue, vEnd, sPath, sDomain, bSecure) {
    if (!sKey || /^(?:expires|max\-age|path|domain|secure)$/.test(sKey)) { return; }
    var sExpires = "";
    if (vEnd) {
      switch (typeof vEnd) {
        case "number": sExpires = "; max-age=" + vEnd; break;
        case "string": sExpires = "; expires=" + vEnd; break;
        case "object": if (vEnd.hasOwnProperty("toGMTString")) { sExpires = "; expires=" + vEnd.toGMTString(); } break;
      }
    }
    document.cookie = escape(sKey) + "=" + escape(sValue) + sExpires + (sDomain ? "; domain=" + sDomain : "") + (sPath ? "; path=" + sPath : "") + (bSecure ? "; secure" : "");
  },
  removeItem: function (sKey) {
    if (!sKey || !this.hasItem(sKey)) { return; }
    var oExpDate = new Date();
    oExpDate.setDate(oExpDate.getDate() - 1);
    document.cookie = escape(sKey) + "=; expires=" + oExpDate.toGMTString() + "; path=/";
  },
  hasItem: function (sKey) { return (new RegExp("(?:^|;\\s*)" + escape(sKey).replace(/[\-\.\+\*]/g, "\\$&") + "\\s*\\=")).test(document.cookie); }
};

// docCookies.setItem("test1", "Hello world!");
// docCookies.setItem("test2", "Hello world!", new Date(2020, 5, 12));
// docCookies.setItem("test3", "Hello world!", new Date(2027, 2, 3), "/blog");
// docCookies.setItem("test4", "Hello world!", "Sun, 06 Nov 2022 21:43:15 GMT");
// docCookies.setItem("test5", "Hello world!", "Tue, 06 Dec 2022 13:11:07 GMT", "/home");
// docCookies.setItem("test6", "Hello world!", 150);
// docCookies.setItem("test7", "Hello world!", 245, "/content");
// docCookies.setItem("test8", "Hello world!", null, null, "example.com");
// docCookies.setItem("test9", "Hello world!", null, null, null, true);

// alert(docCookies.getItem("test1"));