box

• NAME
• FEATURES
• INSTALLATION
• SYNOPSIS
• DESCRIPTION
  • Why?
  • Why not?
• EXPORTS
  • default
  • Box<T>
    • Static Methods
      • constructor
      • Box.of
    • Instance Methods
      • map
      • tap
      • then
      • value
• DEVELOPMENT
• COMPATIBILITY
• SEE ALSO
• VERSION
• AUTHOR
• COPYRIGHT AND LICENSE

NAME

Box - put a value in a box

FEATURES

• no dependencies
• < 170 B minified + gzipped
• fully typed (TypeScript)
• CDN builds (UMD) - jsDelivr, unpkg

INSTALLATION

$ npm install @chocolatey/box

SYNOPSIS

import $ from '@chocolatey/box'

$(42)                    // Box<42>
$(42).value()            // 42
$(42).map(it => it + 1)  // Box<43>
$(42).tap(console.log)   // Box<42>
$(42).then(it => it + 1) // 43
$(42, it => it + 1)      // 43

// "*.tar.gz" -> "*.gz"
const untar = name => $(name)
    .map(it => it.split('.'))
    .tap(it => it.splice(1, 1))
    .then(it => it.join('.'))

untar('package.tar.gz') // "package.gz"

DESCRIPTION

Box puts a value in a container which exposes a handful of methods to facilitate piping values through a series of functions.

It provides a lightweight implementation of the box pattern, which allows the right-to-left flow of function composition to be expressed via the left-to-right syntax of method chaining familiar from jQuery, Lodash, promises etc.

compose

import R from 'ramda'

const fn1 = value => baz(bar(foo(value)))
const fn2 = R.compose(baz, bar, foo)

box

import $ from '@chocolatey/box'

const fn = value => $(value).map(foo).map(bar).then(baz)

Why?

Because:

composition and dot chaining are the same, and dot chaining is more ergonomic in JavaScript

— Brian Lonsdorf

Why not?

If you're using Babel, pipelines can be written natively with features such as the pipeline operator, do expressions and partial application, e.g.:

import { tap } from 'lodash'

const untar = name =>
    name.split('.')
        |> tap(#, it => it.splice(1, 1))
        |> #.join('.')

If you're already using Lodash/Underscore or similar, you can use their built-in methods to implement pipelines, e.g.:

import _ from 'lodash'

const untar = name =>
    _(name)
        .split('.')
        .tap(it => it.splice(1, 1))
        .join('.')

EXPORTS

default

• Type:
  • <T, R>(value: T, fn: (value: T) => R): R
  • <T>(value: T): Box<T>
• Aliases: $, box

import $ from '@chocolatey/box'

$(42)               // Box<42>
$(42, it => it + 1) // 43

The default export is a function which either takes a value and puts it in a box (via Box.of) or takes a value and a function and applies the function to the value.

The latter provides a convenient shorthand for passing an argument to an IIFE, e.g.:

imperative

const counter = (function () {
    let count = 0
    return () => ++count
})()

counter() // 1
counter() // 2
counter() // 3

IIFE

const counter = (function (count) { return () => ++count })(0)

Box

const counter = $(0, count => () => ++count)

Box<T>

Static Methods

constructor

• Type: new <T>(value: T) => Box<T>

import { Box } from '@chocolatey/box'

const box = new Box(42) // Box<42>

Creates a new Box instance containing the supplied value.

Box.of

• Type: <T>(value: T) => Box<T>

import { Box } from '@chocolatey/box'

const box = Box.of(42)              // Box<42>
const boxes = [1, 2, 3].map(Box.of) // [Box<1>, Box<2>, Box<3>]

Returns a new Box instance containing the supplied value.

Note that of is a function which returns a Box instance rather than a method which returns an instance of its invocant, so the following are equivalent:

class MyBox extends Box {} // XXX missing `of` override

const array = [1, 2]

array.map(it => Box.of(it))   // [Box<1>, Box<2>]
array.map(it => MyBox.of(it)) // [Box<1>, Box<2>]
array.map(Box.of)             // [Box<1>, Box<2>]
array.map(MyBox.of)           // [Box<1>, Box<2>]

Instance Methods

map

• Type: <U>(fn: (value: T) => U): Box<U>

import $ from '@chocolatey/box'

$(42).map(it => it + 1) // Box<43>

Applies the supplied function to the value and returns a new box containing the result.

tap

• Type: (fn: (value: T) => void): this

import $ from '@chocolatey/box'

$(42).tap(console.log) // Box<42>

Applies the supplied function to the value and returns the original box (the invocant). Useful to insert side effects, logging etc. into a pipeline without changing the value.

then

• Type: <U>(fn: (value: T) => U): U

import $ from '@chocolatey/box'

$(42).then(it => it + 1) // 43

Returns the result of applying the supplied function to the value.

value

• Type: (fn?: (value: T) => void): T

import $ from '@chocolatey/box'

$(42).value()            // 42
$(42).value(console.log) // 42

Returns the value. If an optional function is supplied, it is applied to the value before the value is returned. This is similar to tap, except the value is returned rather than the box.

DEVELOPMENT

NPM Scripts

The following NPM scripts are available:

• build - compile the library for testing and save to the target directory
• build:doc - generate the README's TOC (table of contents)
• build:release - compile the library for release and save to the target directory
• clean - remove the target directory and its contents
• rebuild - clean the target directory and recompile the library
• repl - launch a node REPL with the library loaded
• test - recompile the library and run the test suite
• test:run - run the test suite
• typecheck - sanity check the library's type definitions

COMPATIBILITY

• Maintained Node.js versions and compatible browsers

SEE ALSO

Libraries

• fcf - a functional alternative to control-flow statements such as if, switch and while
• fp-ts - functional programming in TypeScript

Videos

• Brian Lonsdorf - Create linear data flow with container style types (Box)
• Brian Lonsdorf - Oh Composable World!

VERSION

1.2.0

AUTHOR

chocolateboy

COPYRIGHT AND LICENSE

Copyright © 2021 by chocolateboy.

This is free software; you can redistribute it and/or modify it under the terms of the MIT license.