Function spliceIn

src/Map.js:837–854

(array, idx, val, canEdit)

}

function spliceIn(array, idx, val, canEdit) {
  const newLen = array.length + 1;
  if (canEdit && idx + 1 === newLen) {
    array[idx] = val;
    return array;
  }
  const newArray = new Array(newLen);
  let after = 0;
  for (let ii = 0; ii < newLen; ii++) {
    if (ii === idx) {
      newArray[ii] = val;
      after = -1;
    } else {
      newArray[ii] = array[ii + after];
    }
  }
  return newArray;
}

function spliceOut(array, idx, canEdit) {
  const newLen = array.length - 1;