overload.ts

function reverse(str: string): string;
function reverse<T>(arr: T[]): T[];
function reverse<T>(stringOrArray: string | T[]): string | T[] {
  if (typeof stringOrArray === "string") {
    return stringOrArray
      .split("")
      .reverse()
      .join("");
  }
  return stringOrArray.slice().reverse();
}

let str = reverse("Pepperoni");
console.log(`String reversed ${str}`);

let arr = reverse(["lol", "what", "hahhue"]);
console.log(`Arr reversed ${arr}`);