grid-neighbors-1d

grid-neighbors-1d

Get the 8 closest neighbors of a grid with edge wrapping from a 1d array

Why?

Usage

Get the neighbors of cell 12 in a 5x5 grid:

import { getNeighbors } from "grid-neighbors-1d";
const neighbors = getNeighbors(12, 5, 5);
console.log(neighbors); // [7, 8, 13, 18, 17, 16, 11, 6] - clockwise from north

getNeighbors returns an array of indexes of the cell immediately to the north of the chosen cell, then clockwise around the remaining cells:

• neighbors[0] = north neighbor
• neighbors[1] = north-east neighbor
• neighbors[2] = east neighbor
• neighbors[3] = south-east neighbor
• neighbors[4] = south neighbor
• neighbors[5] = south-west neighbor
• neighbors[6] = west neighbor
• neighbors[7] = north-west neighbor

This means you can use destructuring if your environment supports it:

const [north, northEast, east, southEast, south, southWest, west, northWest] = getNeighbors(4, 10, 6);

A Direction object is also available for convenience:

import { Direction } from "grid-neighbors-1d";
const neighbors = getNeighbors(12, 5, 5);
console.log(neighbors[Direction.NORTH]); // 7

If memory usage is not a concern and you are likely to call getNeighbors many times, you may want to precalculate the neighbors for a given grid size:

import { generateNeighborLookup } from "grid-neighbors-1d";
const getNeighbors = generateNeighborLookup(5, 5);
const neighbors = getNeighbors(12);
console.log(neighbors); // [7, 8, 13, 18, 17, 16, 11, 6]

For your convenience, TypeScript type declarations (index.d.ts), a declaration map (index.d.ts.map), and a sourcemap (index.js.map) are included.

License

© 2019-23 P. Hughes. All rights reserved.

Shared under the MIT license.

Changelog

2.1.0

• Added generateNeighborLookup to precalculate neighbors when the function will be called many times with the same grid dimensions
• Improved edge case handling