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Chaining into lazy compound functions
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This is small function chaining library that allows one to synthesize units of computation. Unlike very popular method chaining, this feels and behaves differently!


One of the main limitations of method chaining is that it's limited to the predefined set of methods. All the user space functions are second class that is usually limiting. This library does not has this limitation as chaining happens on arbitrary functions:

function descriptor(source) {
  return Object.getOwnPropertyNames(source).reduce(function(result, name) {
    result[name] = Object.getOwnPropertyDescriptor(source, name)
    return result
  }, {})

function merge() {
  var sources =
  var target = sources.shift()
  var whitelist = {}
  sources.forEach(function(source) {
    var properties = descriptor(source)
    Object.keys(properties).forEach(function(name) {
      whitelist[name] = properties[name]
  return Object.defineProperties(target, whitelist)

function pick() {
  var names =
  var source = names.shift()
  var properties = descriptor(source)
  var whitelist = {}
  names.forEach(function(name) {
    whitelist[name] = properties[name]
  return Object.create(Object.getPrototypeOf(source), whitelist)

var synthesize = require("synthesize")

var hash = (synthesize)
 (merge, { x: 12, y: 13 })
 (pick, 'a', 'b', 'x')
 ({ a: 1, b: 2, c: 3, d: 4 })


Another key difference is that intermidiate values are not computed during chaining, instead chaining creates synthesize functions that can be invoked to perform all the chained computations.

var t = (synthesize)
  (merge, { x: 12, y: 13 })
  (pick, 'a', 'b', 'x')

typeof(t)                     // => function
t({ a: 1, b: 2, c: 3, d: 4 }) // => { x: 12, a: 1, b: 2 }


Since result of chaining is just an ordinary function, they can be further synthesizeed, or used in any other kind of functional composition.

function method(name) {
  return function methodCall(target) {
    return target[name].apply(target,, 1))

var t1 = (synthesize)
  (method("replace"), "A", "X")

t1("a b c")     // => "X B C"

var t2 = (synthesize)
  (method("split"), " ")
  (method("join"), "-")

t2("a b c")     // => "X-B-C"


npm install synthesize
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