Array.prototype.copyWithin()

const array1 = ["a", "b", "c", "d", "e"];

// Copy to index 0 the element at index 3
console.log(array1.copyWithin(0, 3, 4));
// Expected output: Array ["d", "b", "c", "d", "e"]

// Copy to index 1 all elements from index 3 to the end
console.log(array1.copyWithin(1, 3));
// Expected output: Array ["d", "d", "e", "d", "e"]

copyWithin(target, start)
copyWithin(target, start, end)

console.log([1, 2, 3, 4, 5].copyWithin(2));
// [1, 2, 1, 2, 3];    2 .

console.log([1, 2, 3, 4, 5].copyWithin(0, 3));
// [4, 5, 3, 4, 5]

console.log([1, 2, 3, 4, 5].copyWithin(0, 3, 4));
// [4, 2, 3, 4, 5]

console.log([1, 2, 3, 4, 5].copyWithin(-2, -3, -1));
// [1, 2, 3, 3, 4]

console.log([1, , 3].copyWithin(2, 1, 2)); // [1, empty, empty]

const arrayLike = {
  length: 5,
  3: 1,
};
console.log(Array.prototype.copyWithin.call(arrayLike, 0, 3));
// { '0': 1, '3': 1, length: 5 }
console.log(Array.prototype.copyWithin.call(arrayLike, 3, 1));
// { '0': 1, length: 5 }
//     '3'  .