Sticky Sentinel Element

Custom element implementation of the technique described in this Google Developers article: https://developers.google.com/web/updates/2017/09/sticky-headers

Documentation is still a work in progress.

Usage

There's a no-config option for simple use cases:

<sticky-sentinel></sticky-sentinel>
<div class="sticky-element"></div>

Style the sticky element based on the stuck state of the sentinel:

sticky-sentinel[stuck] ~ .sticky-element {
  /* Add your stuck styles here. */
}

You can also reference the target element explicitly and set a class on it directly when it becomes stuck:

<sticky-sentinel target="sticky_element" stuck-class="stuck"></sticky-sentinel>
<div id="sticky_element"></div>

.sticky-element.stuck {
  /* Add your stuck styles here. */
}

Important: The sentinel must be placed such that its top edge lines up with the top edge of the sticky element. The easiest way to do this is to place the sticky element directly after the sentinel as a sibling.