bowling.js

var Game = function Game() {
  this.marks = [];
};

Game.prototype.add_mark = function add_mark(pins) {
  this.marks.push(pins);
};

Game.prototype.score = function score() {

  var score = 0;

  marks = this.marks.slice(0); // Lets clone to not mess it up.

  while (marks.length > 0)
  {
    score += this._score_frame(marks);
    if(score === 300) break; // Nasty.
  }
  console.log(score);
}


Game.prototype._score_frame = function _score_frame(marks) {

  var current_points = marks.shift();
  if (current_points < 10)
  {
    if(marks.length > 0) {
      current_points += marks.shift();
      if (current_points === 10)
      {
        if(marks.length > 0) current_points += marks[0];
      }
    }
  } else {
    if (marks.length >= 1) current_points += marks[0];
    if (marks.length >= 2) current_points += marks[1];
  }
  return current_points;
}

// example usage
var game = new Game();
game.add_mark(5);
game.score();     //=> 5

game.add_mark(5);
game.score();     //=> 10

game.add_mark(3);
game.score();     //=> 16