To map array last item with JavaScript, we check the items’ index in the map callback.

For instance, we write

const newRows = row.map((rank, i, row) => {
  if (i + 1 === row.length) {
    // Last one.
  } else {
    // Not last one.
  }
});

to call row.map to check if index i + 1 is row.length.

If it is, then the callback is called on the last item in row.

Otherwise, it’s not called on the last object.