.js

function drawGrid(){
	for (var i = 0; i < cols; i++) {
		for (var j = 0; j < rows; j++) {
			grid[i][j].draw() //grid is a 2D array of nodes
		}
	}
}

//inside node class
	draw(){
		if(this.active)
			fill(255, 0, 0)
		else
			fill(255)
		rect(this.x * this.size, this.y * this.size, this.size, this.size)
	}