[DreamTheater]

var calculator = {
  
  readValues: function() {
    this.a = "90";
    this.b = "30";
  },
  
  sum: function() {
    return this.a + this.b;
  },

  mul: function() {
    return this.a * this.b;
  }

  
};
  
  
calculator.readValues();
alert( calculator.hasOwnProperty("a") );