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.

npm install 2d-array-rotation

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

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

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 ]
 * ]
 */

• arr (Array): a two-dimensional array

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

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]
 * ]
 */

• arr (Array): a two-dimensional array

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

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 ]
 * ]
 */

• arr (Array): a two-dimensional array

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

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

• 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.

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.

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],
 * ]
 */

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 ]
 * ]
 */

npm test

• 2.1.0
  • updated dependencies
• 2.1.1
  • updated dependencies

Created by Jon Stout. Licensed under the MIT license.

u/Epyo on Reddit.