Print chess board. Alternate solution. Demo: https://codepen.io/anon/pen/qyezvX

chess_board.html

<pre id="output"></pre>
<script>
	var n = prompt("Enter value of N", 5), c = 1, str = "";

	for(i = 1; i<=n; i++) {
	  if(i % 2 === 0) c = 2;
	  else c = 1;
	  
	  for(j = 1; j<=n; j++) {
		if(c % 2 !== 0) str += "#";
		else str += "&nbsp;"
		
		c += 1;
	  }
	  
	  str += "<br />";
	}

	document.getElementById("output").innerHTML = str;
</script>