How can I add an element to the array at an index of my choosing while altering the array size accordingly?

Question

I have an array that looks something like this:

uint256[] array = [1,2,3,4,5,6,7,8];

I am familiar with how to add an element to an array using array.push(100); which would make the array look like this:

[1,2,3,4,5,6,7,8,100];

How can I add an element to the array at an index of my choosing while altering the array size accordingly?

For instance, how do I add an element to the array at: index [3] or more specific array[3] = 999 while also increasing the size of the array accordingly?

The desired result would look something like this:

[1,2,3,999,4,5,6,7,8,100];

Answer 1

It looks like this has been answered here

I do see that this answer only applies to calldata, however. Here is my "top of brain" naive / brute force approach.

pseudo code:

function sliceNDice(string[] originalArr, uint replaceAtIndex, string insertMe) internal pure {
  tmpArr = [];
  for (let i=0; i < originalArr.length; i++) {
    if (i == replaceAtIndex) {
      tmpArr.push(insertMe);
      tmpArr.push(originalArr[i]);
    } else {
      tmpArr.push(originalArr[i]);
    }
  }
  return tmpArr;
}

// use like
sliceNDice(['foo', 'bar', 'baz'], 1, 'foobarbaz'); // ['foo', 'foobarbaz', 'bar', 'baz']

This is a super brute method and the code above certainly has syntax errors and can be improved (one push for example). I just wanted to give you an alternative way to think about this problem. Good luck!