Array moveItemTo method

Hi Friends, i commonly used function like this

function moveIndexOfArray(arr, indexFrom, indexTo)
arr.splice(indexTo, 0, arr.splice(indexFrom, 1)[0]);

It would be convenient for the method to do it natively and thus avoid this, what do you think?
ex: myArray.moveIndexTo(... or something like this

You can solve the performance problem using copyWithin:

function moveIndexOfArray(arr, indexFrom, indexTo) {
  let temp = arr[indexFrom]
  let source = indexFrom, dest = indexTo 
  if (source < dest) { source = indexTo; dest = indexFrom }
  arr.copyWithin(source, source + 1, dest)
  arr[indexTo] = temp

(This is of course untested and might not be 100% correct, but you get the gist.)

Edit: it's also worth noting that not even C++ has a "move item" or "move index" method for its vectors, nor does it have anything that does that in its <algorithms> library.

Actually C++ has std::rotate which is a more generic way to do this, i.e. you rotate left or right (depending on indexFrom < indexTo) by 1.

1 Like

Thank you again Claudia!

Oh, I missed that. Also worth noting Java has it indirectly (they explain how to do it in the docs for the method), and Rust likewise supports it indirectly via slice.rotate_{left,right}(mid) + subslice syntax. But Python has no such method for lists nor binary sequences, nor does it have anything of use in its builtins or its itertools module - you'd necessarily have to roll it yourself.

+1 for a rotate function, I frequently use it in my project related to music theory (I am currently using arr.concat(arr).slice(index, index + arr.length), which has a bad performance (though I don’t care much)).