Untitled

function Console() {
  console.log(123);
}

var a = Console();

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>

<body>

  <script src="bundle.js"></script>

</body>

</html>

function Console() {
  console.log(123);
}

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>

<body>

  <script src="bundle.js"></script>

  <script>
    var a = new Console();
  </script>

</body>

</html>

(function () {

function yourConstructor() {/* your code */};

window.yourConstructor = yourConstructor;

})();