Если кому-то ещё понадобится
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#block {
width: 25px;
height: 25px;
background-color: red;
position: relative;
}
</style>
</head>
<body>
<div id="block"></div>
<script>
window.onload = function () {
var left = 0;
var top = 0;
document.onkeydown = function (){
var block = document.getElementById("block");
switch (event.keyCode) {
case 39: //вправо
left = left + 10;
block.style.left = left + 'px';
break;
case 37: //влево
left = left - 10;
block.style.left = left + 'px';
break;
case 38: //вверх
top = top - 10;
block.style.top = top + 'px';
break;
case 40: //вниз
top = top + 10;
block.style.top = top + 'px';
break;
}
}
}
</script>
</body>
</html>