function Calc(num1, num2, color) {
   this.num1 = parseInt(num1);
   this.num2 = parseInt(num2);
   this.color = color.toString();

   this.add = function() {
     return this.num1 + this.num2;
   }

   this.substract = function() {
     return this.num1 - this.num2;
   }
}

var x = new Calc(2, 3, 'Black');
var y = new Calc(3, 4, 'Red');
console.log(x.add());
console.log(y.substract());

var x = { a: function () { ... }, b: function() { ... } ... } ;
這方法似乎不行用new.