data.task

    3.1.2 • Public • Published

    Data.Task

    Build statusNPM versionDependencies statusLicenceStable API

    The Task(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.

    Example

    var Task = require('data.task')
    var fs = require('fs')
     
    // read : String -> Task(Error, Buffer)
    function read(path) {
      return new Task(function(reject, resolve) {
        fs.readFile(path, function(error, data) {
          if (error)  reject(error)
          else        resolve(data)
        })
      })
    }
     
    // decode : Task(Error, Buffer) -> Task(Error, String)
    function decode(task) {
      return task.map(function(buffer) {
        return buffer.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 Task.
    var concatenated = intro.chain(function(a) {
                         return outro.map(function(b) {
                           return a + b
                         })
                       })
     
    // But the implementation of Task is pure, which means that you'll
    // never observe the effects by using `chain` or `map` or any other
    // method. The Task 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.
    concatenated.fork(
      function(error) { throw error }
    , function(data)  { console.log(data) }
    )

    Installing

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

    $ npm install data.task
    

    Using with CommonJS

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

    var Task = require('data.task')

    Using with AMD

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

    require(['data.task'], function(Task) {
      ( ... )
    })

    Using without modules

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

    <script src="/path/to/data.task.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://github.com/folktale/data.task.git
    $ cd data.task
    $ npm install
    $ make bundle
    

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

    Documentation

    You can read the documentation online or build it yourself:

    $ git clone git://github.com/folktale/data.task.git
    $ cd data.task
    $ npm install
    $ make documentation
    

    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 :)

    Licence

    Copyright (c) 2013-2015 Quildreen Motta.

    Released under the MIT licence.

    Install

    npm i data.task

    DownloadsWeekly Downloads

    4,533

    Version

    3.1.2

    License

    MIT

    Unpacked Size

    18.3 kB

    Total Files

    12

    Last publish

    Collaborators

    • killdream
    • robotlolita