why is `M` not defined on line 59?

gaussian_elimination.js

function * count() {
    const maximum =
        (arguments.length === 1 && typeof arguments[0] === "number") ? arguments[0] :
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("maximum")) ? arguments[0].maximum :
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("max")) ? arguments[0].max :
        (arguments.length === 2 || arguments.length === 3) ? arguments[1] : 0;
    
    const minimum =
        (arguments.length === 1 && typeof arguments[0] === "number") ? 0 :
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("minimum")) ? arguments[0].minimum :
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("min")) ? arguments[0].min :
        (arguments.length === 2 || arguments.length === 3) ? arguments[0] : 0;
    
    const increment =
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("increment")) ? arguments[0].increment :
        (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0].hasOwnProperty("inc")) ? arguments[0].inc :
        (arguments.length === 3) ? arguments[2] : (maximum > minimum ? 1 : -1);
    
    for (let i = 0, I = (Math.max(minimum, maximum) - Math.min(minimum, maximum)) / Math.abs(increment); i <= I; i++) {
        yield i * increment + minimum;
    }
}
function swap (A, h, k) {
    for (let i = 0, I = M; i < I; i++)
    {
        A[h][i] = A[h][i] ^ A[k][i];
        A[k][i] = A[k][i] ^ A[h][i];
        A[h][i] = A[h][i] ^ A[k][i];
    }
}

{
    const A =
        [ [  2, -1,  0 ],
          [ -1,  2, -1 ],
          [  0, -1,  2 ] ];
    
    const N = A.length;
    const M = A[0].length;
    /* */
    let h = 0;
    let k = 0;
    
    for (let h = 0, H = M; h < H; h++) {
    for (let k = 0, K = N; k < K; k++) {

            const i_max = [...count(h, M - 1)]
                .map((i, n) => [ Math.abs(A[i][k]), n ])
                .reduce(($0, $1) => $0[0] > $1[0] ? $0 : $1)[1];

            if (A[i_max, k] === 0) {
                k = k + 1;
            }
            else
            {
                swap(A, h, i_max);
            }

            for (let i = h + 1, I = M; i < I; i++) {
                f = A[i][k] / A[h][k];

                A[i][k] = 0;

                for (let j = k + 1, J = N; j < J; j++) {
                    A[i][j] = A[i][j] - A[h][j] * f;
                }
            }
            
            h = h + 1;
            k = k + 1;
        }
    }
}