Makes checker. Pass in size of square

Checker.js

function makeChecker(size=1) {
	const black = '#000000'
	const white = '#FFFFFF'
	const w = canvas.width/size
	const h = canvas.height/size

	let yColor = black
	// let yColor = white
	for(let y=0; y<h; y++) {
		yColor = (yColor===black) ? white : black
		let prev = null
		let curr = null
		for(let x=0; x<w; x++) {
			if(!curr) {
				curr = yColor
			}else{
				prev = curr
				curr = (prev===black) ? white : black
			}
			ctx.fillStyle = curr
			ctx.fillRect(x*size, y*size, size, size);
		}
	}
}