lcp.njk

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 Copyright 2020 Google LLC
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
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 See the License for the specific language governing permissions and
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-->
{% extends 'layout.njk' %}

{% block content %}
  <h1 elementtiming="main-heading">LCP Test</h1>
  <p>
    {% if not imgDelay %}
      {% set imgDelay = 500 %}
    {% endif %}
    <img elementtiming="main-image" {% if imgHidden %}hidden{% endif %} src="/test/img/square.png?delay={{ imgDelay }}">
  </p>
  <p>Text below the image</p>

  <p><a id="navigate-away" href="https://example.com">Navigate away</a></p>

  <!-- Include a tall element to ensure scrolling is possible. -->
  <div style="height: 100vh"></div>

  <footer>Text below the full-height element.</footer>

  <script type="module">
    function jsonifyEntry(entry) {
      return {
        element: entry.element.nodeName.toLowerCase(),
        size: entry.size,
        startTime: entry.startTime,
      };
    }

    const {onLCP} = await __testImport('{{ modulePath }}');

    onLCP((lcp) => {
      // Log for easier manual testing.
      console.log(lcp);

      // Elements can't be serialized, so we convert first.
      lcp.entries = lcp.entries.map(jsonifyEntry);

      if (lcp.attribution && lcp.attribution.lcpEntry) {
        lcp.attribution.lcpEntry = jsonifyEntry(lcp.attribution.lcpEntry);
      }

      // Test sending the metric to an analytics endpoint.
      navigator.sendBeacon(`/collect`, JSON.stringify(lcp));
    }, {reportAllChanges: self.__reportAllChanges});
  </script>
{% endblock %}