LazyChain

Document | js | d.ts

FRP(Functional reactive programming) supporting DSL. Lazy stream, monad, pattern match, guard implements in JavaScript.

Data-Oriented Design by Pipeline

mainstream
[input]
  |     substream(async)
  | ----> |
  |       :     procstream
  |       | ----> |
  |       |       |
  |       | <---- |
  |       |
  |       |     ajax(async)
  |       | ----> |
  |       |       :
  |       | <---- |
  |       |
  |       |     worker(async)
  |       | ----> |
  |       |       :
  |       | <---- |
  |       |
  |       |     process
  |       | ----> |
  |       |       |
  |       | <---- |
  |       |
  | <---- |
  |
[output]

var streams = build({
  main: LazyChain(),
  sub: LazyChain(),
  proc: LazyChain()
});

streams.main.notify('');

function build(streams) {
  streams.proc
    .map(encodeURI);

  streams.sub
    .lazy()
    .stream(streams.proc)
    .lazy(req)
    .filter(isXHR)
    .map(conv);

  streams.main
    .stream(streams.sub)
    .stream(alert);

  return streams;
}

function req(v) {
  return $.ajax(v);
}

function isXHR(v) {
  return v instanceof Object;
}

function conv(xhr) {
  return xhr.responseText;
}

// Double dispatch by pattern match
class A {
  constructor(public val?) {
  }
  type = 1
}
class B {
  constructor(public val?) {
  }
  type = 2
}

var f = LazyChain.dispatcher<A|B, string>([
    [<A|B>{ val: 0 }],
    _ => 'val 0'
  ], [
    [<A|B>{ val: Number }],
    _ => 'val Number'
  ], [
    [A],
    _ => 'A'
  ], [
    [<B>{ type: 2 }],
    _ => 'type 2'
  ], [
    [B],
    _ => 'B'
  ]);

f(new A());  // 'A'
f(new B());  // 'type 2'
f(new A(0)); // 'val 0'
f(new A(1)); // 'val Number'

// Asynchronous method chain
LazyChain([1, 2])
  .lazy(function (v, i, a, e, d) { setTimeout(function () { d.resolve(v * 2) }, 50) }, true)
  .map(function (v) { return v * 3 })
  .lazy(function (v, i, a, e, d) { setTimeout(function () { d.resolve(v * 10) }, 50) }, true)
  .reduce(function (r, v, i, a) { return r + v }, 0)
  .forEach(function (v) {
    console.log(v); // 180 = (1 * 2 * 3 * 10) + (2 * 2 * 3 * 10)
  });

LazyChain($.ajax(''))
  .filter(function (v) { return 'object' === typeof v })
  .forEach(function (xhr) {
    console.log(xhr); // XHR object
  });
LazyChain(true);
['./']
  .lazy(function (v) { return $.ajax(v) })
  .filter(function (v) { return 'object' === typeof v })
  .forEach(function (xhr) {
    console.log(xhr); // XHR object
  });
LazyChain(false);

// Stream generate and control
var a = LazyChain(),
    b = LazyChain();

LazyChain(a)
  .stream('number', b)
  .stream(function (v, i, a, e) {
    console.log(v); // 0
  });

a.notify(0, '');
b
  .stream(function (v, i, a, e) {
    console.log(typeof v); // string
  });

// Maybe
var Just = Number,
    Nothing = Error;
 
LazyChain<number>([-1, 0, 1, NaN])
  .pattern([
    Number, n => n > 0,
    n => Just(n)
  ], [
    Number,
    _ => Nothing()
  ], [
    void 0,
    _ => Nothing()
  ])
  .pattern([
    Just,
    n => Just(n * 100)
  ])
  .pattern([
    Just,
    n => console.log(Just, n) // 1
  ], [
    Nothing,
    e => console.log(Nothing, e)
  ]);

// Either
type Either = [number, number|typeof Number];
type EitherValue = [number, number];
var LEFT: Either =
      [1, Number],
    Left =
      (data: number) => <EitherValue>[LEFT[0], data],
    RIGHT: Either =
      [0, Number],
    Right =
      (data: number) => <EitherValue>[RIGHT[0], data],
    Either = {
      return: Right,
      bind: (m: EitherValue, f: typeof Right|typeof Left) => <EitherValue>f.apply(undefined, [m[1]]),
      fail: _ => Left(NaN)
    };
var monad =
  LazyChain<number>()
    .monad<Either>(Either, false)
    .monadic([
      RIGHT,
      data => Right(data + 1)
    ], [
      LEFT,
      data => Left(data)
    ]);
var stream =
  LazyChain<number>();
stream
  .monad<Either>(Either)
  .stream(monad)
  .monadic([
    RIGHT,
    function (data) {
      console.log(data); // 1
      return Right(data);
    }
  ]);
stream.notify(0);

Extend

Underscore.js / Lo-Dash

LazyChain([1, 2, 3], _)
  .stream(function (v) {
    console.log(v); // 1, 2, 3
  })
  .difference([1, 3])
  .stream(function (v) {
    console.log(v); // 2
  });

Installation

npm i lazychain

Documentation

API

Spec

Sorry, japanese documents only. I welcome translation.

Browser

• IE9+
• Chrome
• Firefox
• Safari
• Android
• iOS

License

MIT License