JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
</head>
<body>
<html>
<input id="inputfield" type="textfield" onkeyup="alert('keyup event')" >
</html>
</body>
</html>

JavaScript

textbox = document.getElementById("inputfield")
textbox.value = "word";

  var evt = document.createEvent("KeyboardEvent");
   
  var keyEventFunction = (evt.initKeyboardEvent ? "initKeyboardEvent" : "initKeyEvent");
  
evt[keyEventFunction](
                   "keyup",
                    true, 
                    true, 
                    window, 
                    false, 
                    false, 
                    false, 
                    false,
                    32, 
                    0 
);

textbox.focus();
textbox.dispatchEvent(evt);