immutable

immutable.js

var Calculator = function (n) {
  this.number = n;
};
　
Calculator.prototype.add = function (c) {
  return new Calculator(this.number + c.number);
};
　
Calculator.prototype.multiple = function (c) {
  return new Calculator(this.number * c.number);
}

var a = new Calculator(4);
var b = new Calculator(2);
var c = new Calculator(0);

var result = a.add(c).multiple(b).add(a.multiple(b)).number;