negative-indexing.ts

declare global {
  interface Array<T> {
    atIndex(index: number): T | undefined;
  }
}

Array.prototype.atIndex = function <T>(index: number): T | undefined {
  if (index < 0) {
    index = this.length + index; // Convert negative index to positive
  }
  return this[index];
};

// Usage example:
const arr = [10, 20, 30, 40, 50];
console.log(arr.atIndex(-1)); // Outputs: 50
console.log(arr.atIndex(-2)); // Outputs: 40
console.log(arr.atIndex(0)); // Outputs: 10