How to write an extension-method in JavaScript

The following code adds a method to the Array object.

Array.prototype.remove = function (index) {
  const temp = [].concat(this);
  return [].concat(temp.slice(0, index)).concat(temp.slice(index + 1));
};

let arr = [0, 1, 2, 3, 4, 5];
console.log(arr.remove(3))

The mechanism works: the remove method returns a new array, different from the original array, in which the element placed at the index index is removed.

I would like to rewrite the remove method so that it modifies the starting array and returns the removed element, just like the Array.prototype.pop method behaves.

    Array.prototype.remove = function (index) {...};
    let arr = [0, 1, 2, 3, 4, 5];
    let removed = arr.remove(3);
    console.log({arr, removed}); // arr: [0, 1, 2, 4, 5], removed: 3

What is the technique to achieve this result?

Using the splice method on the array to remove one item on that index.
The splice method will return an array with removed items ( which in our situation is is just an array with one item ), you can access the item by index 0

Array.prototype.remove = function (index) {
  const removedItems = this.splice(index, 1);
  return removedItems[0];
};

As @jsejcksn shared, for Typescript

interface Array<T> { remove(index: number): T | undefined; }