Javascript Program to find which key press at keyboard

This is the basic javascript to find the ASCII code of key-code value 

<script type="text/javascript">
function displayunicode(e){
var unicode=e.keyCode? e.keyCode : e.charCode
alert(unicode)
}
</script>
<form>
<input size="2" maxlength="1" onkeyup="displayunicode(event); this.select()"/>
</form>

Example: Enter a key below: