Display a prompt box which ask the user for her/his name, and output a message:


 The html looks like this
<html>
<head>
<script language="JavaScript">
function showInput() {
    var message = 'Hello ' + document.getElementById("person").value;
    document.getElementById('display').innerHTML = message;
}
</script>
</head>
<body>
 <form>
<label><b>Please enter your name</b></label>
<input type="text" name="person" >
</form>

<input type="submit" onclick="showInput();"><br />

<p><span id='display'></span> </p>
</body>
</html>
See javascript - display html form values in same page after submit - Stack Overflow
Example 1