Fills a block with zeros given the block number, hardcoded for a sudoku grid.

fill-block.js

// Fills a block with zeros given the block number, hardcoded for a sudoku grid.
// The "grid" must be a lineal array and must have 81 elements exactly.

// how to use it...
let grid = fillBlock(sudokuStoreMock.grid, 4);

function fillBlock(grid, blockNumber) {
    let newGrid = grid.slice(0, grid.length);
    blockNumber = blockNumber || 0;

    let startPoints = [0, 3, 6, 27, 30, 33, 52, 55, 58];

    /*
     *      0   3   6
     *      27  30  33
     *      52  55  58
     */

    let pointer = startPoints[blockNumber];

    for (let index = 0; index < 9; index += 1) {
        newGrid[pointer] = 0;
        if ((pointer + 1) % 3 === 0 && pointer !== startPoints[blockNumber]) {
            pointer = pointer + 6;
        }
        pointer++;
    }

    return newGrid;
}