<!doctype html> <meta charset="utf-8"> <title>Imperative slotting API: Invalidation on re-assignment</title> <link rel=help href="https://bugzilla.mozilla.org/show_bug.cgi?id=1752694"> <link rel=match href="imperative-slot-layout-invalidation-001-ref.html"> <link rel=author href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez"> <link rel=author href="https://mozilla.org" title="Mozilla"> <div id="host"> <span>one</span> </div> <script> let host = document.getElementById("host"); function assignFirstChild() { host.shadowRoot.querySelector("slot").assign(host.firstElementChild); } host.attachShadow({ mode: "open", slotAssignment: "manual" }).innerHTML = "<slot>Fallback</slot>"; assignFirstChild(); host.getBoundingClientRect(); host.insertAdjacentHTML("afterbegin", "<span>two</span>"); assignFirstChild(); </script>