the-hangman.js

String.prototype.replaceAt = function(index, character) {
    return this.substr(0, index) + character + this.substr(index + character.length);
};

function Hangman(word){
  this.lives = 7;
  this.word = word;
  this.try = this.try.bind(this);
  this.characters = [];
  this._buildProgress();
};

Hangman.STATUS = {
  DIED: 'dead',
  SAVED: 'saved'
}

Hangman.prototype = {
  lives: NaN,
  status: null,
  word: null,
  _progress: null,
  characters: null
};

Hangman.prototype._buildProgress = function(){
  if(typeof this.word !== 'string')
      return undefined;

  this._progress = '';
  for(var i=0; i<this.word.length; i++){
    this._progress+= "_";
  }

  this.characters = this.word.split('');
};

Hangman.prototype.try = function(character){
  if (this.status === Hangman.STATUS.SAVED || this.status === Hangman.STATUS.DIED)
    return undefined;

  if(typeof character !== 'string')
    return undefined;

  var index = this.word.indexOf(character);
  if(index !== -1 && this.characters.indexOf(character) !== -1){
    var indices = [];
    for(var i=0; i<this.word.length; i++) {
      if (this.word[i] === character) indices.push(i);
    }

    for (var i=0; i<indices.length; i++){
      this.characters.splice(this.characters.indexOf(character), 1);
      this._progress = this._progress.replaceAt(indices[i], character);
    }

    if (this.characters.length === 0)
      this.status = Hangman.STATUS.SAVED;

    return true;
  }

  this.lives--;
  if (this.lives === 0)
    this.status = Hangman.STATUS.DIED;

  return false;
};

Hangman.prototype.progress = function(){
  return this._progress;
};

Hangman.prototype.status = function(){
  return this._status;
};