<!DOCTYPE html>
<html>
<head>
</head>
<body>
<p>
<input type="text" id="demo" placeholder="type some key">
</p>
<p>
<textarea id="area" rows="10" cols="25"></textarea>
</p>
<script>
var input = document.getElementById('demo');
var area = document.getElementById('area');
input.onkeydown = handle;
var lastTime = Date.now();
function handle(e) {
var text = ' keyCode=' + e.keyCode + "\n";
if (area.value && Date.now() - lastTime > 250) {
area.value += new Array(81).join('-') + '\n';
}
lastTime = Date.now();
area.value += text;
area.scrollTop = area.scrollHeight;
if (form.elements[e.type + 'Stop'].checked) {
e.preventDefault();
}
}
</script>
</body>
</html>