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node_modules/stylelint/lib/utils/isCustomElement.mjs

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+import svgTags from 'svg-tags';
+
+import mathMLTags from './mathMLTags.mjs';
+
+/**
+ * Check whether a type selector is a custom element
+ *
+ * @param {string} selector
+ * @returns {boolean}
+ */
+export default function isCustomElement(selector) {
+	if (!/^[a-z]/.test(selector)) {
+		return false;
+	}
+
+	if (!selector.includes('-')) {
+		return false;
+	}
+
+	const selectorLowerCase = selector.toLowerCase();
+
+	if (selectorLowerCase !== selector) {
+		return false;
+	}
+
+	if (svgTags.includes(selectorLowerCase)) {
+		return false;
+	}
+
+	if (mathMLTags.includes(selectorLowerCase)) {
+		return false;
+	}
+
+	return true;
+}