It is possible to do this, in particular for checkRow, checkColumn, as follows:

• Add the following function

  function checkCells(rowFirst, rowLast, colFirst, colLast) {
    for (let row = rowFirst; row < rowLast; row++) {
      for (let col = colFirst; col < colLast; col++) {
        let index = toLinearIndex(row, col);
        if (board[index] !== markers[player]) return false;
      }
    }
    return true;
  }
  ```
  

• Update checkRow

  function checkRow(row) {
    return checkCells(row, row + 1, 0, numCols);
  }
  

• Update checkCol

  function checkColumn(col) {
    return checkCells(0, numRows, col, col + 1);
  }
  

To use checkCells for checking major/minor diagonal, we need to employ a more complex (and convoluted) logic.

The changes already make for a less readable code and a more complex and convoluted checkCells will change this situation for the worse. My preference would be keeping the code as is (without using checkCells at all).