chaining_pattern.js

var Calc = function(init){
  this.init = init;
}

Calc.prototype.equals   = function(callback){
  callback(this.init);
}

Calc.prototype.add  = function(val){
  this.init  += val;
  return this;
}

Calc.prototype.minus  = function(val){
  this.init  -= val;
  return this;
}

Calc.prototype.multiply  = function(val){
  this.init  *= val;
  return this;
}

Calc.prototype.divide  = function(val){
  this.init  /= val;
  return this;
}

var calc =  new Calc(0);

calc.add(1)
  .minus(0)
  .multiply(2)
  .divide(2)
  .equals( function(result){ console.log(result)} );