matrix-determinant.js

const determinant = m => {
  const l = m.length;
  if (l === 1) return m[0][0];
  if (l === 2) return m[0][0] * m[1][1] - m[1][0] * m[0][1];

  let result = 0;
  for (let i = 0; i < l; i++) {
    result += Math.pow(-1, i) * m[0][i] * determinant(minor(m, i, 0));
  }
  return result;
};

const minor = (m, i, j) => 
  m.map(e => e.filter((_, index) => index !== i))
    .filter((_, index) => index !== j);