headache.js

// returns itself
var self = function(object) {
  return object
}

var get = function(name) {
	// returns a property of an object
	return function(object) {
		return object[name]
	}
}

var call = function(fn) {
	// apply a function on the object
	var rest = Array.prototype.slice.call(arguments, 1)
	return function(object) {
		return fn(object).apply(object, rest)
	}
}

var send = function(name) {
	var rest = Array.prototype.slice.call(arguments, 1)
	return call.apply(this, [get(name)].concat(rest))
}

// ==== selector functions ====
var max = function(criteria) {
	return function(current, best) {
		return criteria(current) > criteria(best)
	}
}

var min = function(criteria) {
	return function(current, best) {
		return criteria(current) < criteria(best)
	}
}

// ==== high level function ====
var pick = function(better, array) {
	var none = {}, best = none
	array.forEach(function(item) {
		if (best === none || better(item, best)) {
			best = item
		}
	})
	return best
}

var sort = function(right, array) {
	var out = array.slice()
	out.sort(function(a, b) {
		return right(a, b) ? 1 : -1
	})
	return out
}

// ==== utility ====
var section = function(name) {
	show('=== ' + name + ' ===')
}

// ==== test code ====
var a = [ 2, 5, 1, 2, 30, 24 ]
section('Simple max & min')
show(pick(max(self), a))
show(pick(min(self), a))

var c = [ "apple", "Banana", "pumpkin", "elephant", "zebra", "bee" ];
section('Simple max & min with string')
show(pick(max(self), c))
show(pick(min(self), c))

section('Simple max & min by length')
var length = get('length')
show(pick(max(length), c))
show(pick(min(length), c))

section('Simple string sort')
show(sort(max(self), c))
show(sort(min(self), c))

section('Sort string by length')
show(sort(max(length), c))
show(sort(min(length), c))

section('Case insensitive sorting')
var caseInsensitive = send('toLowerCase')
show(sort(max(caseInsensitive), c))
show(sort(min(caseInsensitive), c))