Implement a connect 4 win detector

connect-four.js

const board = [[t, f, t, f], [f, f, f, f], [f, f, f, f], [f, t, f, f]];

/*
  0 1 2 3 4 5 6 7 8
0 O O O O O O O O B      B = Winning col
1 X O O O A O O O B
2 O X O O O A O O B
3 O O X O O O A O B
4 O O O X O O O A O       X and A = Winning DownRight Diagonals
5 O O O O O O O O A
6 O O O O O O O E O
7 O Y Y Y Y O E O O         Y = Winning row
8 O O O O O E O O O
9 O O O O E O O O O       E = Winning DownLeft Diagonal
*/
const determineDiagonalAnchor = (x, y) =>
  // dr: y = x+b
  // dr: b = y - x
  // dr: x = y - b
  // dl: y = -x+b
  // dl: b = y + x
  // dl: x = b - y
  ({
    dr: [y - (y - x), y - x],
    dl: [y + x - x, y + x],
  });

const aggregateBoard = board =>
  Object.values(
    board.reduce(
      (acc, row, y) =>
        row.reduce((acc2, slot, x) => {
          const {dr: drAnchor, dl: dlAnchor} = determineDiagonalAnchor(x, y);
          const winSets = [
            `column${x}`,
            `row${y}`,
            `drDiag${drAnchor}`,
            `dlDiag${dlAnchor}`,
          ];

          winSets.forEach(set => {
            if (!acc2[set] || !Array.isArray(acc2[set])) {
              acc2[set] = [];
            }
            acc2[set].push(slot);
          });

          return acc2;
        }, acc),
      {},
    ),
  );
// [ [true, false, true, false] ]

const hasContiguousElements = num => result =>
  result.reduce((cont, slot) => {
    if (cont.length >= num) return cont;
    if (slot === false) return [];
    return [...cont, slot];
  }, []).length >= num;

const isWinner = aggregateBoard(board).some(hasContiguousElements(4));