The NPO tag has a method page
that should be called to generate a pageview.
This has to be done for both a synchronous or asynchronous script tag.
<script src="//assets.npo-data.nl/tag/v3/npotag.js"></script>
<script>
NPO.page();
</script>
Or
<script>
document.addEventListener('npoReady', function () {
NPO.page();
});
</script>
<script src="//assets.npo-data.nl/tag/v3/npotag.js" async></script>
To simplify some implementations, an option to generate pageviews automatically has been provided. This is documented in the “Adding the script” section.