JSLinqHelper.NonEnumerable("LastOrDefault",
    function <T>(this: T[], selector?: (item: T, index: number) => boolean): T | null {
        if (!selector) return this.length > 0 ? this[this.length - 1] : null;

        let result = null;
        let i = this.length;

        while (i--) {
            const item = this[i];
            if (selector(item, i) === true) {
                result = item;
                break;
            }
        }

        return result;
    });