iframe-loading-lazy-to-eager.html

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This WPT test may be referenced by the following Test IDs:
- /html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-to-eager.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<head>

  <title>Below-viewport iframes with loading='lazy' load when set to

         loading='eager' or the `loading` attribute is removed</title>

  <link rel="author" title="Dom Farolino" href="mailto:domfarolino@gmail.com">

  <link rel="help" href="https://github.com/whatwg/html/pull/5579">

  <script src="/resources/testharness.js"></script>

  <script src="/resources/testharnessreport.js"></script>

</head>

<script>

  const t = async_test("Below-viewport iframes with loading='lazy' load when " +

                       "set to loading='eager' or the `loading` attribute is " +

                       "removed");

  const iframe_1_onload = t.unreached_func("#iframe_1 should not load before " +

                                           "the window load event");

  const iframe_2_onload = t.unreached_func("#iframe_2 should not load before " +

                                           "the window load event");

  window.addEventListener("load", t.step_func(() => {

    const iframe_1 = document.querySelector('#iframe_1');

    const iframe_2 = document.querySelector('#iframe_2');

    const iframe_1_promise = new Promise((resolve, reject) => {

      iframe_1.onerror = reject;

      iframe_1.onload = resolve;

});

    const iframe_2_promise = new Promise((resolve, reject) => {

      iframe_2.onerror = reject;

      iframe_2.onload = resolve;

});

    Promise.all([iframe_1_promise, iframe_2_promise])

      .then(t.step_func_done())

      .catch(t.unreached_func("The iframes should load successfully"));

    // Kick off the requests.

    iframe_1.loading = 'eager';

    iframe_2.removeAttribute('loading'); // unset the attribute, putting it in

                                         // the default (eager) state.

  }));

</script>

<body>

  <div style="height:1000vh;"></div>

  <iframe id="iframe_1"

          src="resources/subframe.html?1"

          loading="lazy" onload="iframe_1_onload();"></iframe>

  <iframe id="iframe_2"

          src="resources/subframe.html?2"

          loading="lazy" onload="iframe_2_onload();"></iframe>

</body>