split_cookie.js

// head>
// ...
<script type="text/javascript">
    /* A/B splitting - Returns either "A" or "B". */
    function getABsplit() {
    var cookieDomain = ".your_domain.ru";
    var cookieName = "gr_split_GLOBAL";
    var cookieExpire = +new Date()+1000*60 * 60 * 24 * 365;

    // get cookie
    var m = (new RegExp(cookieName+"=([^;]*)")).exec(document.cookie);
    var splitVal = (m == null ? null : unescape(m[1]));

    if (splitVal == "A" || splitVal == "B") {return splitVal}
    splitVal = (Math.random() < 0.5) ? "A" : "B";

    // set cookie
    document.cookie =
    cookieName + "=" + escape(splitVal) +
    ";expires=" + new Date(cookieExpire).toUTCString()+
    ";path=/" +
    ((cookieDomain != null) ? ";domain=" + cookieDomain : "");

    return splitVal;
}
</script>
// ....
// </head>


    // using gravity set cookie
    if ($.cookie('gr_split_GLOBAL') != "A") {

        _gravity.push({
            type: 'recommendation',
            callback: callback_fn,
            numberLimit: 5,
            scenarioId: "ITEM_PAGE",
            currentRegionId: 0,
            currentItemId: 287265,
            resultNames: ["itemId"]
        });
    };