Dice notation roller

dice.js

var dice = function(d) { 
  var a = d.split('d'),
  result = 0,
  num = (typeof (a[0]-0) === 'number') ? a[0] : 1,
  op = (a[1].match(/[\-\+]/)),
  max = (op === null) ? a[1] : a[1].split(op[0])[0],
  mod = (op !== null) ? op[0] + ' ' + a[1].split(op[0])[1] : '';
  for (var i = num; i >= 0; i--) { 
    result += (Math.floor(Math.random() * (max)) + 1)
  }
  return new Function('return ' + result + mod)();
}