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

Example 1

Example 1a
Name:


Note:
JavaScript does not have native (built in) input or output routines. Instead it relies on the facilities provided by its host environment (e.g.web browser).

 The html looks like this
 
<!DOCTYPE html>
<html>
<body>

<p>Click the button to demonstrate the prompt box.</p>

<button onclick="myFunction()">Start</button>

<p id="demo"></p>

<script language="JavaScript">
function myFunction() {
    var person = prompt("Please enter your name", "");
    if (person != null) {
        document.getElementById("demo").innerHTML =
        "Hello " + person;
    }
}
</script>

</body>
</html>
See:
See Example 1b
Javascript Window prompt() Method | w3schools.com
dom - JavaScript get input text value - Stack Overflow
Javascript