Another Deep Freeze

This utility will recursively make the Object/Array and all it's properties/items immutable.

Javascript provides a built-in utility (Object.freeze) for freezing objects but it only freezes immediate properties of the object. If a property's depth is greater than 1 it will still remain mutable.

Installation

NPM

npm i -S another-deep-freeze

Yarn

yarn add another-deep-freeze --save

Usage

Pass the object to deepFreeze and generate an immutable clone.

import deepFreeze from 'another-deep-freeze'

const txn = {
  _id: 1,
  amount: 1000.0,
  branch: {
    _id: 1,
    tellers: [1, { _id: 2, code: 'XYZ001' }]
  }
}

// freeze txn in a cloned object
const frozenTxn = deepFreeze(txn)

txn === frozenTxn // false

The following operations will throw TypeError

// 1. mutating existing key
frozenTxn._id = 2
// 2. adding new key
frozenTxn.newKey = 1
// 3. deleting a key
delete forzenTxn.branch
// same behaviour at all depths
frozenTxn.branch._id = 2
// even for an array
frozenTxn.branch.tellers.push(0)
// or an array of objects
frozenTxn.branch.tellers[1].code = 'NEWCODE'

// the prototypes are immutable and any attempt of mutation will throw TypeError
Object.setPrototypeOf(frozenTxn, { foo: 'baz' })
txn.branch.__proto__.foo = 'baz'
txn.branch.tellers.__proto__.length = 0

You may also perform in-place deep freeze.

import deepFreeze from 'another-deep-freeze'

const txn = {
  _id: 1,
  amount: 1000.0,
  branch: {
    _id: 1,
    tellers: [1, { _id: 2, code: 'XYZ001' }]
  }
}

const sameTxn = deepFreeze(txn, /* in-place deep freeze*/ true)

sameTxn === txn // true

This will make txn immutable at all depths.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update the tests as appropriate.

License

MIT