Run last async script

<html>
<head>
<script data="async" src="https://pastebin.com/raw/Xx5ymUy4" async></script>
<script data="async" src="https://pastebin.com/raw/EW7bK8ch" async></script>
<script data="async" src="https://pastebin.com/raw/yMz7HBd8" async></script>
</head>
<body>

<script>
let count = document.querySelectorAll('script[data="async"]').length, calls = 0;
let f = () => {alert('Нужная функция')}
window.callback = () => {
    calls++;
    if (calls >= count) {
        f();
    }
}
</script>

</body>
</html>