get neighbor coordinates from 4 sides and 4 corners

getNeighbors.js

class Grid {
  constructor(rows, columns) {
    this.rows = rows;
    this.columns = columns;
  }
  
  getNeighbors(row, column) {
    let neighbors = [];

    if (!this.isValidCoord(row, column)) {
      return undefined;
    }

    let top = this.getTop(row, column);
    let topRight = this.getTopRight(row, column);
    let right = this.getRight(row, column);
    let bottomRight = this.getBottomRight(row, column);
    let bottom = this.getBottom(row, column);
    let bottomLeft = this.getBottomLeft(row, column);
    let left = this.getLeft(row, column);
    let topLeft = this.getTopLeft(row, column);

    if (top) {
      neighbors.push(top);
    }
    if (topRight) {
      neighbors.push(topRight);
    }
    if (right) {
      neighbors.push(right);
    }
    if (bottomRight) {
      neighbors.push(bottomRight);
    }
    if (bottom) {
      neighbors.push(bottom);
    }
    if (bottomLeft) {
      neighbors.push(bottomLeft);
    }
    if (left) {
      neighbors.push(left);
    }
    if (topLeft) {
      neighbors.push(topLeft);
    }

    return neighbors;
  }

  getTop(row, column) {
    let y = row - 1;
    let x = column;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getTopRight(row, column) {
    let y = row - 1;
    let x = column + 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getRight(row, column) {
    let y = row;
    let x = column + 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getBottomRight(row, column) {
    let y = row + 1;
    let x = column + 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getBottom(row, column) {
    let y = row + 1;
    let x = column;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getBottomLeft(row, column) {
    let y = row + 1;
    let x = column - 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getLeft(row, column) {
    let y = row;
    let x = column - 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  getTopLeft(row, column) {
    let y = row - 1;
    let x = column - 1;

    if (this.isValidCoord(y, x)) {
      return [y, x];
    }

    return undefined;
  }

  isValidCoord(y, x) {
    if (y >= 0 && y < this.rows && x >= 0 && x < this.columns) {
      return true;
    }
    return false;
  }
}

let grid1 = new Grid(2, 3);
console.log('grid1 size rows', grid1.rows, 'columns', grid1.columns);
grid1.getNeighbors(5, 3);


// Example Grid
// (0,0) | (0,1) | (0,2) | (0,3)   
// ------------------------------    
// (1,0) | (1,1) | (1,2) | (1,3)
// ------------------------------
// (2,0) | (2,1) | (2,2) | (2,3)