JavaScript used to simulate a die roll

roll.js

/**
 *  Expects input in the standard format- 1d6+2 or 1d12-1 or 4d4
 */
function roll(dieCode) {
  var total = 0;
  
  var results = dieCode.match(/([0-9]+)d([0-9]+)([\-\+][0-9]+)?/);
  if(results !== null) {
    for(var i = 0; i < parseInt(results[1]); i++) {
      total += Math.floor(Math.random() * parseInt(results[2])) + 1;
    }
    if(parseInt(results[3])) {
      total += parseInt(results[3]);
    }
  }
  return total;
}