Hello World, pure JavaScript

<!DOCTYPE html>
<html>
  <body>
    <h1>Hello World with pure JavaScript</h1>
    Write some text in textbox:
    <input id="hello-input" type="text" />
    <h2 id="hello-output">Hello </h2>
    
    <script>
      var inputField = document.getElementById('hello-input');
      var label = document.getElementById('hello-output');
      
      var handleKeyup = function() {
        var value = inputField.value;
        label.innerHTML = 'Hello ' + value;
      }
      
      if (document.addEventListener) {
        document.addEventListener('keyup', handleKeyup);
      } else if (document.attachEvent) {
        document.attachEvent('keyup', handleKeyup);
      }
    </script>
  </body>
</html>

// Code goes here

/* Styles go here */