JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
	<head>
	</head>
	<body>
    
		<script>
    	alert(local_var); // undefined (good)
      
      let elem = document;
      
      elem.dispatchEvent(new CustomEvent("init")); // not working
    </script>
    
		<script type="module">
      function addEvent(elem, type, handler) {
        if (elem.addEventListener){
          elem.addEventListener(type, handler);
        } else {
          elem.attachEvent("on" + type, handler);
        }
      }

      function draw() {
        alert("do smth");
      }

      let local_var = "not seen",
          elem = document; // example

      addEvent(elem, "init", function () {
        draw();
      });
    </script>
	</body>
</html>