Selectors

To select data from a grid instance, gridl provides some selector function, which allow you to access data like cell values, columns, rows, subgrids or neighbouring cells.

Select a cell at a certain x,y position in the grid.

import {createGridFromArray2D, selectCell} from "gridl/core";

const grid = createGridFromArray2D([
    [0,  1,  2,  3],
    [4,  5,  6,  7],
    [8,  9, 10, 11],
]);

// get the cell value at position = {x: 1, y: 2}
selectCell({grid, x: 2, y: 1}); // => 6

Selecting a column

Select a column at a certain x-position in the grid.

import {createGridFromArray2D, selectColumn} from "gridl/core";

const grid = createGridFromArray2D([
    [  0,   1,   2,   3],
    [  4,   5,   6,   7],
    ["x", "x", "x", "x"],
]);

// get the column at x = 2
selectColumn({grid, x: 2}); // => [2, 6, "x"]

Selecting a row

Select a row at a certain y-position in the grid.

import {createGridFromArray2D, selectRow} from "gridl/core";

const grid = createGridFromArray2D([
    [0,  1,  2,  3],
    [4,  5,  6,  7],
    [8,  9, 10, 11],
]);

// get the row at y = 1
selectRow({grid, y: 1}); // => [4, 5, 6, 7];

Selecting a sub grid

The sub grid selector allows you to extract a certain area of a grid as a new grid instance. The area is specified by x, y, columnCount and rowCount values.

import {createGridFromArray2D, selectSubGrid} from "gridl/core";

const grid = createGridFromArray2D([
    [  0,   1,   2,   3],
    [  4,   5,   6,   7],
    ["x", "x", "x", "x"],
]);

selectSubGrid({grid, x: 1, y: 1, columnCount: 2, rowCount: 2});
// returned subgrid (which is a new grid instance):
// {
//     x: 1,
//     y: 1,
//     cellCount: 4,
//     columnCount: 2,
//     rowCount: 2,
//     array2D: [
//         [  5,   6],
//         ["x", "x"],
//     ],
// }

Selecting neighbouring cells

Select some or all neighbouring cells of a certain cell in the grid. By default, the selector returns all surrounding neighbours. This can be changed by providing a list of positions with the optional positions property.

import {
    createGridFromArray2D,
    selectSubGrid,
    NorthWest,
    North,
    NorthEast,
    OrthogonalDirections,
} from "gridl/core";

const grid = createGridFromArray2D([
    [0,  1,  2,  3],
    [4,  5,  6,  7],
    [8,  9, 10, 11],
]);

// get all neighbouring cells around the origin at position {x: 1, y: 0}
selectNeighbours({grid, origin: {x: 1, y: 0}});
// => [
//     {cell:  1,  position: {x: 1, y: 0}},
//     {cell:  2,  position: {x: 2, y: 0}},
//     {cell:  6,  position: {x: 2, y: 1}},
//     {cell: 10,  position: {x: 2, y: 2}},
//     {cell:  9,  position: {x: 1, y: 2}},
//     {cell:  8,  position: {x: 0, y: 2}},
//     {cell:  4,  position: {x: 0, y: 1}},
//     {cell:  0,  position: {x: 0, y: 0}},
// ]

// get orthogonal neighbours only (North, East, South, East)
selectNeighbours({grid, origin: {x: 1, y: 1, positions: OrthogonalDirections}});
// => [
//     {cell: 1,  position: {x: 1, y: 0}},
//     {cell: 6,  position: {x: 2, y: 1}},
//     {cell: 9,  position: {x: 1, y: 2}},
//     {cell: 4,  position: {x: 0, y: 1}},
// ]

// select top neighbours only
const topNeighbourPositions = [NorthWest, North, NorthEast];
selectNeighbours({grid, origin: {x: 2, y:1}, positions: topNeighbourPositions});
// => [
//     {cell: 1,  position: {x: 1, y: 0}},
//     {cell: 2,  position: {x: 2, y: 0}},
//     {cell: 3,  position: {x: 3, y: 0}},
// ]