preload/modulepreload-json.html

<!doctype html>
<meta charset=utf-8>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<script>
function attachAndWaitForLoad(element) {
    return new Promise((resolve, reject) => {
        element.onload = resolve;
        element.onerror = reject;
        document.body.appendChild(element);
    });
}

promise_test(function(t) {
    const link = document.createElement('link');
    link.rel = 'modulepreload';
    link.as = 'json';
    link.href = 'resources/dummy.json';
    return attachAndWaitForLoad(link).then(() => {
      const absoluteURL = new URL(link.href, location.href).href;
      assert_equals(performance.getEntriesByName(absoluteURL).length, 1, absoluteURL);
    });
}, 'link rel=modulepreload with as=json should preload JSON module');
</script>