How to lazy load new Google Adsense code using JS

Google has replaced

<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js</script>

with

<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-1234567890123456" crossorigin="anonymous"</script>

ref: Google Adsense Announcement

Old Adsense Code was like:

<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-XXXXXXXXXXXXXXXX"
     crossorigin="anonymous"></script>
<ins class="adsbygoogle"
     style="display:inline-block;width:350px;height:90px"
     data-ad-client="ca-pub-XXXXXXXXXXXXXXXX"
     data-ad-slot="XXXXXXXXXX"></ins>
<script>
     (adsbygoogle = window.adsbygoogle || []).push({});
</script>

New Adsense Code is like:

<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-XXXXXXXXXXXXXXXX"
     crossorigin="anonymous"></script>
<ins class="adsbygoogle"
     style="display:inline-block;width:350px;height:90px"
     data-ad-client="ca-pub-XXXXXXXXXXXXXXXX"
     data-ad-slot="XXXXXXXXXX"></ins>
<script>
     (adsbygoogle = window.adsbygoogle || []).push({});
</script>

Old JS code to load the Ad after the page load is complete was:

    <script type="text/javascript">
        function downloadJSAtOnload() {
        var element = document.createElement("script");
        element.src = "https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js";
        document.body.appendChild(element);
        }
        if (window.addEventListener)
        window.addEventListener("load", downloadJSAtOnload, false);
        else if (window.attachEvent)
        window.attachEvent("onload", downloadJSAtOnload);
        else window.onload = downloadJSAtOnload;
    </script>

As ?client=ca-pub-xxxxxx" crossorigin="anonymous" is added in script tag of new Ad Code, now what would be the new JS code to load the ads?

Well This is not really lazy load This is defer loading and not recommended, but here you go

<script>
function downloadJSAtOnload() {
    var element = document.createElement("script");
    element.src = "https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-XXXXXXXXXXXXXXXX";
    element.async = true;
    element.setAttribute('crossorigin', 'anonymous');
    document.body.appendChild(element);
}
if (window.addEventListener)
    window.addEventListener("load", downloadJSAtOnload, false);
else if (window.attachEvent)
    window.attachEvent("onload", downloadJSAtOnload);
else window.onload = downloadJSAtOnload;
</script>

If you are looking for lazy load AdSense check out Lazy Loading Adsense