Mutate a copy of data without changing the original source. Inspired by immutability-helper.

Downloads in past


700.0.46 years ago6 years agoMinified + gzip package size for immutability-util in KB


Mutate a copy of data without changing the original source. Inspired by kolodny/immutability-helper / ProtoTeam/immutability-helper-x and rewrite with ES6 syntax for convenient API and higher performance.

Build Status Coverage Status npm npm download

  1. Features

Features or key points.
  1. Use chainble API to mutate a copy of object.
  2. Simplify your code by finding target to be updated with path string.
  3. Maybe can optimize your web app with a bit higher performance.

  1. Install & Usage

Install with NPM.
npm install -S immutability-util

Then use it.
const iu = require('immutability-util');
// or 
import iu from 'immutability-util';

// obj need to be mutated.
var obj = {
  a: 1,
  b: 2,
  c: {
    d: 3,
    e: {
      f: [4, 5, 6],
      g: {
        h: 'iu',
    i: {
      j: 'hello, world.',
      k: [7, 8, 9],
      l: [10, 11, 12],

// chainable usage.
const state = iu(obj)
  .$apply(['a'], v => v + 1)
  .$merge(['c', 'e', 'g'], { m: 'update'})
  .$push(['c', 'e', 'f'], [7, 8, 9])
  .$set(['c', 'i', 'j'], 'hello node 8.')
  .$splice(['c', 'i', 'k'], [[1, 1, 10]])
  .$unset(['c'], ['d'])
  .$unshift(['c', 'i', 'l'], [13])
  .value(); // then get the mutated copy.
// or use path string.
iu(obj).$set('c.i.j', 'hello node 8.').value();

And process array like this:
const obj = {
  a: {
    b: [{
      c: [1, 2, 3],
    }, {
      d: 4,
    }, {
      e: [5, 6],
const state = iu(obj)
  .$apply('a.b[1].d', v => v + 1)
  .$push('a.b[0].c', [4])
  .$set('a.b[2].e[0]', 'hello node 8.')

  1. Available API

After got the instance of ImmutabilityUtil, you can use the chainable methods below.
- $apply(path, function): passes in the current value to the function and updates it with the new returned value. - $merge(path, object): merge the keys of object with the target. - $push(path, array): push() all the items in array on the target. - $set(path, any): replace the target entirely. - $splice(path, array of arrays): call splice() with the array of arrays on the target with the parameters provided by the item. - $unset(path, array of strings): remove the list of keys in array from the target object. - $unshift(path, array): unshift() all the items in array on the target.
~Also you can use API update(), and put spec into it, just like immutability-helper.~
Then you can use API value() to get the immutable data copy. All the value of method are compatible with immutability-helper.
Your pull requests are needed for more API.

  1. Build & Test

You can develop and test as below.
npm run build
# run the testcases
npm run test

You can run npm run benchmark to get the comparison of performance.

  1. License