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Clarify create an element assertion #1485

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annevk merged 2 commits into from
Jul 15, 2026
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Clarify create an element assertion #1485

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Clarify create an element assertion
annevk Jul 8, 2026
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use a list
annevk Jul 15, 2026
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26 changes: 24 additions & 2 deletions dom.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -6954,8 +6954,30 @@ null, or a {{CustomElementRegistry}} object <var>registry</var> (default "<code>
<li><p>Set <var>result</var> to the result of <a>constructing</a> <var>C</var>, with no
arguments.

<li><p>Assert: <var>result</var>'s <a for=Element>custom element state</a> and
<a for=Element>custom element definition</a> are initialized.
<li>
<p><a for=/>Assert</a>: <var>result</var>'s <a for=Element>custom element state</a> is
"<code>custom</code>" and its <a for=Element>custom element definition</a> is non-null,
<var>result</var>'s <a for=Element>custom element state</a> is "<code>precustomized</code>",
or <var>result</var>'s <a for=Element>custom element state</a> is neither
"<code>custom</code>" nor "<code>precustomized</code>" and its
<a for=Element>custom element definition</a> is null.

@domfarolino domfarolino Jul 15, 2026

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nit: slightly prefer https://github.com/whatwg/html?tab=contributing-ov-file#common-mistakes-around-prose-style:~:text=When%20nesting%203%2B%20conditions%20in%20a%20list for this many conditions.


<div class=example id=example-return-override>
<pre><code class=lang-javascript>
customElements.define("x-example", class extends HTMLElement {
constructor() {
// Non-conformant: returns an existing element instead of calling super().
return document.createElement("p");
}
});

document.createElement("x-example");
</code></pre>

<p>Here <var>result</var> is the <code>p</code> <a for=/>element</a>, whose
<a for=Element>custom element state</a> is "<code>uncustomized</code>" and whose
<a for=Element>custom element definition</a> is null.
</div>

<li>
<p>Assert: <var>result</var>'s <a for=Element>namespace</a> is the <a>HTML namespace</a>.
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