Edit in JSFiddle

var M1 = $M([
  [1,7,3],
  [9,4,0],
  [2,7,1]
]);

var M2 = $M([
  [6,2,8],
  [9,1,3],
  [0,7,6]
]);

var M = M1.x(M2);

document.getElementById('result').innerHTML = M;