lcp.njk

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 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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-->
{% extends 'layout.njk' %}

{% block content %}
  <h1>LCP Test</h1>
  <p>
    {% if not imgDelay %}
      {% set imgDelay = 500 %}
    {% endif %}
    <img {% 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">
    import {getLCP} from '{{ modulePath }}';

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

      // Elements can't be serialized, so we convert first.
      lcp = {
        ...lcp,
        entries: lcp.entries.map((e) => ({
          element: e.element.nodeName.toLowerCase(),
          size: e.size,
          startTime: e.startTime,
        })),
      };

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