array-immutable

Immutable JavaScript Array class.

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The existing JavaScript Array class has a problem.

Some of its built-in methods support modern concepts, others don’t. Some methods leave source arrays unchanged (immutable 👍), others change arrays in-place (mutable 👎). Some methods are pure functions (no side effects 👍), others are un-pure (has side effects 👎). In addition, some methods that should return an array don’t (can't do method chaining 👎).

array-immutable addresses all of these Array problems by creating a clas named ArrayI (the letter 'I' stands for "immutable"). It's identical to Array, except all the un-pure Arraymethods that modify arrays in-place have been replaced with pure functions that don't modify the source array, returning instead a copy (deep or shallow).

array-immutable methods behave in a consistent way, eliminating the need to remember if a given method modifies in place or not.

Installation

$ npm install array-immutable

Usage

Node.js:

// from a node.js module
const ArrayI = require('array-immutable');

HTML:

<!-- from a browser file -->
<script src="arrayi.js"></script>
 
<!-- minified version -->
<script src="arrayi.min.js"></script>

Creating Arrays

Create a new array with new ArrayI()

// ArrayI:
const myArray = new ArrayI('a', 'b', 'c');
// ArrayI ['a', 'b', 'c']
 
// vs. Array:
const myArray = new Array('a', 'b', 'c');
// [ 'a', 'b', 'c' ]

Or with ArrayI.from()

// ArrayI:
const myArray = ArrayI.from("hello");
// ArrayI [ 'h', 'e', 'l', 'l', 'o' ]
 
// vs. Array:
const myArray = Array.from("hello");
// [ 'h', 'e', 'l', 'l', 'o' ]

Or with ArrayI.of()

// ArrayI:
const myArray = ArrayI.from(['cows', 'pigs', 'goats']);
// ArrayI ['cows', 'pigs', 'goats']
 
// vs. Array:
const myArray = ArrayI.from(['cows', 'pigs', 'goats']);
// ['cows', 'pigs', 'goats']

Or from an existing Array with ArrayI.arrayI()

const oldArray = [1,2,3,'a'];
const newArray = ArrayI.arrayI(oldArray);
// ArrayI [1, 2, 3, 'a']

Configuration

ArrayI defaults to deep copying of all arrays. Change this to shallow copying with ArrayI.deepCopy().

All of the Array methods are available in ArrayI, with all the same input parameters. There are two new static functions.

Static Functions

ArrayI.arrayI()

The arrayI() static function creates a new ArrayI from an existing array.

Syntax

ArrayI.arrayI(array);

Parameters

array - an array

Return value

A new ArrayI array.

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ArrayI.deepCopy()

Toggle between deep and shallow copy modes, or obtain current mode.

Syntax

ArrayI.deepCopy([deep]);

Parameters

deep [optional] - true for deep copy, false for shallow, blank to obtain current mode

Return value

The existing copy mode: true for deep copy, false for shallow

Functions that Return New Arrays

The following functions return new ArrayI arrays:

• .from()
• .of()
• .prototpye.concat()
• .prototype.copyWithin()
• .prototype.fill()
• .prototype.filter()
• .prototype.flat()
• .prototpye.flatMap()
• .prototype.pop()
• .prototype.push()
• .prototype.reverse()
• .prototype.shift()
• .prototype.slice()
• .prototype.sort()
• .prototype.splice()
• .prototype.unshift()

Functions That Return Differently than Array

Some of the existing Array functions modify an array in-place, but return something other than the changed array.

Since immutability require all functions that modify arrays to return array copies, the following ArrayI methods return array copies instead of what Array returns:

• .prototype.pop() (Array returns removed element)
• .prototype.push() (Array returns new length of array)
• .prototype.shift() (Array returns removed element)
• .prototype.slice() (Array returns array of removed elements)
• .prototype.shift() (Array returns removed element)
• .prototype.splice() (Array returns array of removed elements)
• .prototype.unshift() (Array returns new length of array)

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Reference

For details on all functions, see the Array documentation:

MDN web docs - Array

License

The MIT License (MIT)

Copyright (c) 2020 Terry Morse

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.