function increment(input) { return input + 1;}
function decrement(input) { return input - 1; }
function double(input) { return input * 2; }
function halve(input) { return input / 2; }

var initial_value = 1;

var pipeline = [ ///behavior we want to capture (in the order we want to use them)
  increment,
  increment,
  increment,
  double,
  increment,
  increment,
  halve
];


var final_value = pipeline.reduce(function(acc, fn) { ///starts at pipeline[0]
  return fn(acc);
}, initial_value);

var reversed = pipeline.reduceRight(function(acc, fn) { ///starts at the last value and work BACKWARDS
  return fn(acc);
}, initial_value)

final_value
reversed