iframe-with-fetch-variants.html

Enable keyboard shortcuts

<!DOCTYPE html>

<meta charset="utf-8" />

<script>

    const url = new URL(new URLSearchParams(location.search.substr(1)).get('url'), location.href);

    const before = performance.now();

    fetch(url)

        .then(r => r.text())

        .then(() =>

            parent.postMessage({

                before,

                after: performance.now(),

                entry: performance.getEntriesByName(url)[0].toJSON()

            }));

</script>