pipeline.js

Pipeline works like the pipe operator more common in functional programming languages, like Elixir.

This lib supports sync and async arguments.

If all arguments are sync functions or literal, the pipeline will run as a normal function returning the last value computed. In case one of the arguments is a function that returns a promise or a promise instance (then-able object), a promise will be returned at the end.

Usage

Sync

function double(x) {
  return x * 2
}

function square(x) {
  return x * x
}

var output = pipeline(
  2,
  double,
  square
)
console.log(output) // => 16

Async

pipeline(
  bookingDetails.userId,
  fetchUserById, // async
  JSON.parse
)
  .then(function(result) {
    console.log(result)
  })
  .catch(function(error) {
    console.log(error)
  })

Mixed

It is also possible to mix sync and async arguments. Whenever a function that generates promises or a promise intance is found, the lib switchs to async mode and will return a Promise.

Installation

To use the library, install it through npm

npm install @caiogondim/pipeline --save

To port it to Browser or any other (non CJS) environment, use your favorite CJS bundler. No favorite yet? Try: Browserify, Webmake or Webpack.

Examples

Validation (sync and async)

// Before
function validateEmail(email) {
  email = trim(email)
  validateEmailTld(email)
  validateEmailFormat(email)
}

// After
function validateEmail(email) {
  return pipeline(
    email,
    trim,
    validateEmailTld,
    validateEmailFormat
  )
}

try {
  validateEmail('[email protected]')
} catch (error) {
  console.log(error)
}

Straight-forward Cases

// Before
if (cache && localStorage.getItem(endpoint)) {
  return m.prop( JSON.parse( localStorage.get(endpoint) ) )
}

// After
if (cache && localStorage.getItem(endpoint)) {
  return pipeline(
    localStorage.get(endpoint),
    JSON.parse,
    m.prop
  )
}

Usage with const

// Before
let items = base64ToJSON(response.data.content)
items = Array.isArray(items) ? items : [items]

// After
const items = pipeline(
  base64ToJSON(response.data.content),
  x => Array.isArray(x) ? x : [x]
)

Functional Updates

// Before
return Event.create(
  Object.assign(attrs, { parent_id: parentId, status: 'draft' })
)

// After
return pipeline(
  Object.assign(attrs, { parent_id: parentId, status: 'draft' }),
  Event.create
)

Reference and credits

• Ramda.js pipe
• lodash.js flow
• pipe.py
• Some exampes taken from https://github.com/mindeavor/es-pipeline-operator/wiki/Example-Use-Cases

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