if (!Array.prototype.indexOf)    {        Array.prototype.indexOf = function(elt)        {            var len = this.length >>> 0;            var from = Number(arguments[1]) || 0;            from = (from < 0)                ? Math.ceil(from)                : Math.floor(from);            if (from < 0)                from += len;            for (; from < len; from++)            {                if (from in this &&                    this[from] === elt)                    return from;            }            return -1;        };    }