[AndrewGSW]

You can still use with IE<9 if you add the following to the top of your code:

if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(elt /*, from*/) {
        var len = this.length;
        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;
    };
}

You should copy this EXACTLY as it is. I believe it's from Mozilla.