<!DOCTYPE html>
<html>

  <script>
    function det(m) // calculate the determinant of the square matrix m
    {
        if (m.length === 2) // if its a 2X2 matrix..
            return m[0][0] * m[1][1] - m[0][1] * m[1][0];
    }

    var matrix = [[1, 2], [3, 4]];
    document.write(det(matrix));// -2
  </script>
  <head>
    <title>Matrix</title>
  </head>
  <body>
  </body>
</html>