Untitled

export default function sum(x, y) {
    return x + y;
}

import { sum } from './mymodule';


window.onload = function () {
    const result = sum(2, 3);
    console.log(result);
};

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>App2</title>
    <link href="css/default.css" rel="stylesheet" />
</head>
<body>
    <div>Content goes here!</div>
    <script src="js/main.js" type="module">
    </script>
</body>
</html>