Humm? Is not your own solution read through the string a lot mor of times? doing a cicle for you are reading the string mor than once for each character.

Shouldn't be any issue with modifying the given parameter as we are told that we "can assume that all inputs are valid integers".

From MDN:
"Parameters are essentially passed to functions by value — so if the code within the body of a function assigns a completely new value to a parameter that was passed to the function, the change is not reflected globally or in the code which called that function.

When you pass an object as a parameter, if the function changes the object's properties, that change is visible outside the function."

He did not do the same thing. The .sort() method has a time complexity of O(n log(n)). This algo can be solved with one simple for loop as seblm described with a time complexity of O(n), which will be far more performant as your array grows in size.

whats the difference than? you did the same thing.

Agree that this shouldn't be considered best practice. Clean code tho.