2d-array-rotation

2d-array-rotation
=================

A collection of functions to rotate the values within a given two-dimensional array (i.e. an Array of Arrays) clockwise by 90, 180 or 270 degrees. Potentially useful for -- say -- manipulating game pieces or sprites, among other possible applications. Provided as an ES6-compatible module.

__Functions__
- rotate90
- rotate180
- rotate270
- rotate
- hflip
- vflip

__Additional Notes__
- Can handle both square (e.g. 3x3) and rectangular (e.g. 3x5, 4x8) two-dimensional arrays. Just make sure that the rows are all the same length; results may be inconsistent otherwise.
- Source arrays are not directly modified.
- Values within rows are re-indexed directly from the source array, not copied or cloned. Object types and references will remain consistent.

Installation

``sh
npm install 2d-array-rotation
`

Usage

$3

#### Via ES6-style imports

`javascript
import {rotate, rotate90} from "2d-array-rotation";
`

#### Via standard node.js requires

`javascript
const rotate = require('2d-array-rotation').rotate;
const rotate90 = require('2d-array-rotation').rotate90;
// and so on
`

$3

#### rotate90(arr)

Rotates the given two-dimensional array 90 degrees clockwise.

`javascript
let i = [
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
];
let o = rotate90(i);
/**
* Result: [
* [ 7, 4, 1 ],
* [ 8, 5, 2 ],
* [ 9, 6, 3 ]
* ]
*/
`

##### Parameters
+ arr (Array): a two-dimensional array

##### Returns
A new two-dimensional Array that represents the rotated form of the input.

#### rotate180(arr)

Rotates the given two-dimensional array 180 degrees clockwise.

`javascript
let i = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[10, 11, 12]
];
let o = rotate180(i);
/**
* Result: [
* [12, 11, 10],
* [ 9, 8, 7],
* [ 6, 5, 4],
* [ 3, 2, 1]
* ]
*/
`

##### Parameters
+ arr (Array): a two-dimensional array

##### Returns
A new two-dimensional Array that represents the rotated form of the input.

#### rotate270(arr)

Rotates the given two-dimensional array 270 degrees clockwise.

`javascript
let i = [
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
];
let o = rotate270(i);
/**
* Result: [
* [ 3, 6, 9 ],
* [ 2, 5, 8 ],
* [ 1, 4, 7 ]
* ]
*/
`

##### Parameters
+ arr (Array): a two-dimensional array

##### Returns
A new two-dimensional Array that represents the rotated form of the input.

#### rotate(arr, deg)

Rotates the given two-dimensional array by the given number of degrees clockwise. Calls rotate90, rotate180, or rotate270, depending on the input.

`javascript
let i = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[10, 11, 12],
[13, 14, 15]
];
let o = rotate(i, 90);
/**
* Result: [
* [13, 10, 7, 4, 1],
* [14, 11, 8, 5, 2],
* [15, 12, 9, 6, 3]
* ]
*/
// note that this function can also handle negative degree values...
let o2 = rotate(i, -270); // returns same as above
// ... and degree values higher than 360
let o3 = rotate(i, 450); // returns same as above
`

##### Parameters
+ arr (Array): A two-dimensional array.
+ deg (Number): Number of degrees to rotate. Must be a multiple of 90, or an error will be thrown.

##### Returns
A new two-dimensional Array that represents the rotated form of the input; or, if told to rotate by 0 or 360 degrees, the original arr itself without any modifications.

#### hflip(arr)

Bonus function -- flips the array horizontally.

`javascript
let input = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[10, 11, 12]
];
let o = hflip(input);
/**
* Result: [
* [3, 2, 1],
* [6, 5, 4],
* [9, 8, 7],
* [12, 11, 10],
* ]
*/
`

#### vflip(arr)

Bonus function -- flips the array vertically.

`javascript
let input = [
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
];
let o = vflip(input);
/**
* Result: [
* [ 7, 8, 9 ],
* [ 4, 5, 6 ],
* [ 1, 2, 3 ]
* ]
*/
`

Testing

`sh
npm test
``

Release History

* 2.1.0
- updated dependencies
* 2.1.1
- updated dependencies

Credits and Licensing

Created by Jon Stout. Licensed under the MIT license.

Special Thanks To

u/Epyo on Reddit.