$.get_guid() generates a globally unique ID(GUID). The get_new flag returns a new id if true, or, by default, returns the previous id.

$.get_guid()

    $.get_guid = function(get_new) {
        get_new = get_new || false;
        if ($.guid === null) {
            $.guid = 0;
        }
        if (get_new) {
            $.guid++;
        }
        return $.guid;
    };