Cascade Reduce

0.0.4 update: This update adds a new function that allows you to chain iterators just by adding them as extra arguments. You no longer need to invoke the iterators one inside the other. The updated function also does not require you to use a special function to create iterators. Here is a use example for 0.0.4:

// the new method is called 'cascadeNoNest'
var reduce = require('cascadeReduce').cascadeNoNest;
 
// it takes an iterator and returns a function
var totalArray = reduce(function(acc, el){
  return acc + el;
})
 
// extra iterators are simply functions that take one element
var onlyEven = function(el){
  return (el % 2 > 0) ? 0 : el
}
 
var timesOneHundred = function(el){
  return (el * 100)
}
 
var timesTwo = function(el){
  return (el * 2)
}
 
/*
when you invoke the reduce function with an array, an accumulator 
and a chain of iterators, each item will pass through the chain from
left to right before being passed into the reduce function
*/
 
totalArray([1,2,3,4], 0, onlyEven, timesOneHundred, timesTwo) //=> 1200
 

Here is the documentation for the original library, which is still available as part of the module:

Cascade Reduce allows you to pass any number of iterators into a reduce function such that each iterator will be invoked with each item in the collection in a chain. There are two functions in this library: cascadeReduce and cascadeIterator.

cascadeReduce

cascadeReduce = function(iterator){
    return function(collection, accumulator, iterator_chain){...};
}

cascadeReduce is a function that takes an iterator and returns a function that takes a collection, an accumulator, and a nested chain of iterators.

cascadeIterator

cascadeIterator = function(iterator){
    return function(item_or_iterator){...}
}

cascadeIterator takes an iterator function and returns a function that can take either another cascadeIterator or an element as its sole argument. Each element from reduce will pass through the iterators, starting with the outermost iterator, and will finally be passed into the iterator that was passed into cascadeReduce.

Use

var reduce = require('cascade-reduce').cascadeReduce;
var iterator = require('cascade-reduce').cascadeIterator;
 
var totalArray = reduce(function(acc, item){
    return (acc + item);
})
 
var onlyEven = iterator(function(item){
    var modTwo = item % 2;
    return (modTwo > 0) ? 0 : item;
})
 
var timesOneHundred = iterator(function(item){
    return (item * 100)
})
 
var timesTwo = iterator(function(item){
    return (item * 2)
})
 
totalArray([1,2,3,4]) //=> 11
totalArray([1,2,3,4], 0, onlyEven) //=> 4
totalArray([1,2,3,4], 0, onlyEven(timesOneHundred)) //=> 400
totalArray([1,2,3,4], 0, onlyEven(timesOneHundred(timesTwo))) //=> 1200