Function isSpecial

lib/html/syntax.js:4045–4050

(/** @type {HtmlElement} */ el)

const HEADING = new Set(["h1", "h2", "h3", "h4", "h5", "h6"]);

const isSpecial = (/** @type {HtmlElement} */ el) => {
	if (el.namespace === NS_HTML) return SPECIAL.has(el.tagName);
	if (el.namespace === NS_MATHML) return MATHML_SPECIAL.has(el.tagName);
	if (el.namespace === NS_SVG) return SVG_SPECIAL.has(el.tagName.toLowerCase());
	return false;
};

// SVG tag name case adjustments (null prototype: looked up with markup-controlled
// names, a plain object would resolve `constructor` etc. to inherited values)