Fast Shallow Array Cloning in Javascript

assets/shim/css.has.mjs

@@ -0,0 +1,9 @@
+// :has() is still missing in many browsers.
+document.querySelectorAll("*").forEach((v, k) => {
+	let s = new Set();
+	for (let c of v.children) {
+		s.add(c.tagName.toLocaleLowerCase());
+	}
+	if (s.size > 0)
+		v.dataset["has"] = Array.from(s.values()).join(" ");
+});