:seedling: Under 1kb, tiny API, zero dependencies.

:+1: Makes all native array methods immutable operations.

:v: Two simple methods $set and $unset for objects and arrays.

:point_right: Built for Node ES2015 environments. Use a bundler, transpiler, and Proxy polyfill as required.

Install

npm install --save mewt

yarn add mewt

Import

// ES2015
import immutable from 'mewt'

// CommonJS
var immutable = require('mewt')

Usage

Create an immutable instance from a JavaScript array or object.

Both objects and arrays have the $set and $unset methods.

const immutableArray = immutable([])
const immutableObject = immutable({})

immutableArray[0] = 'Van Morrison' //=> Error "array is immutable"
immutableObject.name = 'Van Morrison' //=> Error "object is immutable"

Array

Use $set and $unset to create new array with applied change.

Use all array instance methods as usual, however those that would normally return a single non-array value (pop, push, shift, unshift) will return an array containing the value and a new array (see part 2 in example below).

const arr = immutable([])

// 1. all array instance methods are available
const arr1 = arr.concat('bubble')

    console.log(arr1) //=> ['bubble']
    console.log(arr1 === arr) //=> false

// 2. methods with non-array return value (push, pop, shift, unshift)
// also return new array, accessible via destructuring
const [val, arr2] = arr1.pop()

    console.log(val) //=> 'bubble'
    console.log(arr2) //=> []
    console.log(arr2 === arr1) //=> false
    
// 3. use $set and $unset to get new array with changes
const arr3 = arr2.$set(0, 'Iggy Pop')
    
    console.log(arr3) //=> ['Iggy Pop']
    console.log(arr3 === arr2) //=> false

Object

Use $set and $unset to create new object with applied change.

const obj = immutable({})

// 1. properties are added/updated using `$set`
const obj1 = obj.$set('album', 'Hunky Dory')

    console.log(obj1) //=> {album: 'Hunky Dory'}
    console.log(obj1 === obj) //=> false

// 2. properties are deleted using `$unset`
const obj2 = obj1.$unset('album')

    console.log(obj2) //=> {}
    console.log(obj2 === obj1) //=> false

Contributors

mewt has received contributions from these wonderful people:

Balázs Édes, Scott Humphries, Michael J. Ryan, Jamie Curtis

Contributing

All pull requests and issues welcome!

If you're not sure how, check out the great video tutorials on egghead.io!