cls.njk

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{% extends 'layout.njk' %}

{% block content %}
  <h1>CLS Test</h1>
  {% if noLayoutShifts %}
    <p>This text does not shift.</p>
  {% else %}
    <p><img src="/test/img/square.png?delay=500" alt="Gray square" /></p>
    <p><img src="/test/img/square.png?delay=1000" alt="Gray square" /></p>
    <p>Text below the images that will get pushed down.</p>
  {% endif %}

  <script type="module">
    import {getCLS} from '/dist/web-vitals.es5.min.js';

    getCLS((cls) => {
      // Log for easier manual testing.
      console.log(cls);

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