The Symmetry of JavaScript Functions (revised) http://raganwald.com/2015/03/12/symmetry.html

examples.js

// Yellow - Decorator for method
function isFruit(name){
 return ['banana', 'apple'].indexOf(name) !== -1;
}
function not(fn){
 return function(){
  return !fn.apply(null, arguments);
 };
}

var names = ['banana', 'chestnut'];
names.filter(isFruit);
names.filter(not(isFruit));

// Blue - Decorator for Functions, aka Object.fn
function Tax(rate){
 this.rate = rate;
}
Tax.prorotype.calculate = function(amount){
 return amount*this.rate;
}
// this won't work for Tax.prototype.calculate
function requireNumberForMethod(fn){
 return function(number){
  if(!Number.isFinite(number)) throw number + ' is not a number';
  return fn.apply(null, number); 
 }
}
function requireNumber(fn){
 return function(number){
  if(!Number.isFinite(number)) throw number + ' is not a number';
  return fn.apply(this, number);
 }
}
Tax.prototype.calculate = requireNumber(Tax.prototype.calculate);
tax = new Tax(0.8);
tax.calculate(100); //=> 8