function countRowShift(logicalRow) {
      // Todo: compare perf between reduce vs sort->each->brake
      return (0, _array.arrayReduce)(removedItems, function (count, removedLogicalRow) {
        var result = count;

        if (logicalRow > removedLogicalRow) {
          result += 1;
        }

        return result;
      }, 0);
    }
Unshift items (remove and shift chunk of array to the left).

@param {Number|Array} physicalIndex Array index or Array of indexes to unshift.
@param {Number} [amount=1] Defines how many items will be removed from an array (when index is passed as number).