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    Build Status NPM version Dependencies Status stable

    The Future(a, b) structure represents values that depend on time. This allows one to model time-based effects explicitly, such that one can have full knowledge of when they're dealing with delayed computations, latency, or anything that can not be computed immediately.

    A common use for this monad is to replace the usual Continuation-Passing Style form of programming, in order to be able to compose and sequence time-dependent effects using the generic and powerful monadic operations.


    var Future = require('data.future')
    var fs = require('fs')
    // read : String -> Future(Error, Buffer)
    function read(path) {
      return new Future(function(reject, resolve) {
        fs.readFile(path, function(error, data) {
          if (error)  reject(error)
          else        resolve(data)
    // decode : Future(Error, Buffer) -> Future(Error, String)
    function decode(buffer) {
      return {
        return a.toString('utf-8')
    var intro = decode(read('intro.txt'))
    var outro = decode(read('outro.txt'))
    // You can use `.chain` to sequence two asynchronous actions, and
    // `.map` to perform a synchronous computation with the eventual
    // value of the Future.
    var concatenated = intro.chain(function(a) {
                         return {
                           return a + b
    // But the implementation of Future is pure, which means that you'll
    // never observe the effects by using `chain` or `map` or any other
    // method. The Future just records the sequence of actions that you
    // wish to observe, and defers the playing of that sequence of actions
    // for your application's entry-point to call.
    // To observe the effects, you have to call the `fork` method, which
    // takes a callback for the rejection, and a callback for the success.
      function(error) { throw error }
    , function(data)  { console.log(data) }


    The easiest way is to grab it from NPM. If you're running in a Browser environment, you can use Browserify

    $ npm install data.future

    Using with CommonJS

    If you're not using NPM, Download the latest release, and require the data.future.umd.js file:

    var Future = require('data.future')

    Using with AMD

    Download the latest release, and require the data.future.umd.js file:

    require(['data.future'], function(Future) {
      ( ... )

    Using without modules

    Download the latest release, and load the data.future.umd.js file. The properties are exposed in the global Future object:

    <script src="/path/to/data.future.umd.js"></script>

    Compiling from source

    If you want to compile this library from the source, you'll need Git, Make, Node.js, and run the following commands:

    $ git clone git://
    $ cd data.future
    $ npm install
    $ make bundle

    This will generate the dist/data.future.umd.js file, which you can load in any JavaScript environment.


    You can read the documentation online or build it yourself:

    $ git clone git://
    $ cd monads.maybe
    $ npm install
    $ make documentation

    Then open the file docs/index.html in your browser.

    Platform support

    This library assumes an ES5 environment, but can be easily supported in ES3 platforms by the use of shims. Just include es5-shim :)


    Copyright (c) 2013-2014 Quildreen Motta.

    Released under the MIT licence.


    npm i data.future

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