William Johnson's Color Scale ( but edited )

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>Bill's Color Scale ( NOT Mine )</title>
	</head>
	<body style="text-align: center;">
		<script>
			var white = 0;
			window.addEventListener("keyup", function(e) {
				if (e.which == 65) {
					var hm = prompt("How many shades do you want to view?");
					var flip = prompt("Go from Light to Dark? (Enter true OR false)");
					var table = document.createElement("table");
					table.style.width = "400px";
					table.style.height = "200px";
					document.body.appendChild(table);
					for (var i = 0; i < 3; i++) {
						if (flip == "false") {
							white = 0;
						} else {
							white = 255;
						}
						window.eval("var row" + i + " = document.createElement('tr')");
						table.appendChild(eval("row" + i));
						for (var l = 0; l <= hm; l++) {
							window.eval("var col" + i + l + " = document.createElement('td');");
							window.eval("col" + i + l).style.width = Math.floor(400 / (hm * 3)) + "px";
							window.eval("row" + i).appendChild(eval("col" + i + l));
							switch (i) {
								case 0:
									window.eval("col" + i + l).style.backgroundColor = "rgb(255," + white + "," + white + ")";
									window.eval("col" + i + l).innerHTML = Math.floor(white);
									if(flip == "false") {
										white += (256 / hm);
									} else {
										white -= (256 / hm);
									}
									break;
								case 1:
									window.eval("col" + i + l).style.backgroundColor = "rgb(" + white + ",255," + white + ")";
									window.eval("col" + i + l).innerHTML = Math.floor(white);
									if(flip == "false") {
										white += (256 / hm);
									} else {
										white -= (256 / hm);
									}
									break;
								case 2:
									window.eval("col" + i + l).style.backgroundColor = "rgb(" + white + "," + white + ",255" + ")";
									window.eval("col" + i + l).innerHTML = Math.floor(white);
									if(flip == "false") {
										white += (256 / hm);
									} else {
										white -= (256 / hm);
									}
									break;
							}
							if (eval("col" + i + l).innerHTML > 256) {eval("col" + i + l).innerHTML = "255";}
							if (eval("col" + i + l).innerHTML < 0) {eval("col" + i + l).innerHTML = "0";}
						}
					}
				}
			});
		</script>
	</body>
</html>