let numCols = 10; // Number of columns

let numRows = 10; // Number of rows

let w, h; // Width and Height of each cell

​

function setup() {

  createCanvas(400, 400);

​

  // Calculate w and h of each cell in relation to width and height of canvas

  w = width / numCols;

  h = height / numRows;

}

​

function draw() {

  background(220);

​

  // For every column

  for (let c = 0; c < numCols; c++) {

    // Calculate x-position of column: How many pixels is it from the left-side of the canvas?

    let x = c * w;

    // For every row

    for (let r = 0; r < numRows; r++) {

      // Calculate y-position of row: How many pixels is it from the top-side of the canvas?

      let y = r * h;

      let add = c + r;

      // Approach 1: If column and row number are both even OR both odd, make it black

      //if(c % 2 == 0 && r % 2 == 0 || c % 2 == 1 && r % 2 == 1) fill('black');

      // Approach 2: If the column and row number add up to an even number, make it black

      //       if((c + r) % 2 == 0) fill('black')

      if (add % 2 == 0) fill("black");

      // Other wise make it white

      else fill("white");

      // Draw the cell

      rect(x, y, w, h);

    }

  }

}

​