extensions.macro 🌌

Extension functions and parameters for JavaScript inspired by Kotlin's extensions

Installation

npm i extensions.macro

Or if using yarn:

yarn add extensions.macro

Then just import:

import extension from 'extensions.macro'

Note that you need to have babel and babel-plugin-macros installed

Motivation

As you might know - providing new properties to JavaScript built-in objects pollutes the global scope and is widely considered unsafe. This macro solves the problem allowing you to use dot notation to access external functions and properties 😋

Examples

Declaring extension

import extension from 'extensions.macro'
extension.String.plus = string => plusString => `${string} ${plusString}`

Note that it's initialized with function witch first argumument( string ) provides an instance it's called on.

Then you can use it like:

'Hello'.plus('Extension!') //Outputs: Hello Extension!

Another example:

import extension from 'extensions.macro'

extension.any.log = obj => () => {
  console.log(obj)
  return obj
}

'The cosmos is yours 🌌'.log()
//Logs: The cosmos is yours 🌌

Usage

extension.<object constructor name>.<extension name> = <init>

Object constructor name

It's the result of calling .constructor.name on object the extension is dedicated for

;(15).constructor.name //Outputs: Number

extension.any...

You can write any instead of constructor name to match any type of object

Extension name

It's the name of the extension you choose

Init

It's the function that takes an object and returns what should extension return

Rules

• Declare extension in module scope
• Extensions do not override object properties
• Be aware of recursive extension

Declare extension in module scope

//...
import curry from '@ramda/curry'

extension.Function.curry = fun => curry(fun) //✔
{
  extension.Function.curry = fun => curry(fun) //❌Throws: Error
}
//...

Extensions do not override object properties

extension.any.reduce = obj => reducer => reducer(obj)

'Who let the dogs out!?'.reduce(v => `${v} wow! wow! wow!`)
//Outputs: Who let the dogs out!? wow! wow! wow!
;[1, 2, 3].reduce((total, value) => total + value)
//Outputs: 6

Be aware of recursive called extension

Though you can do it but it does not very performant and is considered to be blocked in future versions

extension.Number.factorial = num => () => {
  if (num === 1 || num === 0) return 1
  return num * (num - 1).factorial()
}
//Works, but it's bad ❗

Do instead:

const factorial = num => {
  if (num === 1 || num === 0) return 1
  return num * factorial(num - 1)
}

extension.Number.factorial = num => () => factorial(num)
//Right way ✅

Other features

Extension overloading

You can overload any extension like so:

extension.any.plus = obj => plusObj => obj + plusObj
extension.String.plus = string => plusString => `${string} + ${plusString}`

'👽'.plus('💩') //Outputs 👽 + 💩
;(5).plus(2) ////Outputs 7

Extension parameters

You might overlook that you needn't return function from extension

extension.Array.last = arr => arr[arr.length - 1]
console.log(['🥞', '💋'].last) //Logs: 💋

To Do

• Add Import and Export feature for extension
• Add more reliable Errors

Proposals

• Add extension setters?