# 2d-array-rotation

Rotates two-dimensional arrays clockwise by 90 degrees, 180 degrees, or 270 degrees

## Usage no npm install needed!

``````<script type="module">
import dArrayRotation from 'https://cdn.skypack.dev/2d-array-rotation';
</script>``````

# 2d-array-rotation

A collection of functions to rotate the values within a given two-dimensional array (i.e. an `Array` of `Array`s) 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

• 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

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

## Usage

### Importing

#### Via ES6-style imports

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

#### Via standard node.js requires

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

### Functions

#### rotate90(arr)

Rotates the given two-dimensional array 90 degrees clockwise.

``````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.

``````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.

``````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.

``````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.

``````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.

``````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

``````npm test
``````

## Release History

• 2.1.0
• updated dependencies
• 2.1.1
• updated dependencies