#3940 refactor check if style is already present

src/compiler/compile/render_dom/index.ts

@@ -45,13 +45,7 @@ export default function dom(
 	if (should_add_css) {
 		body.push(b`
 			function ${add_css}(customStyleTag) {
-				const styleId = "${component.stylesheet.id}-style"
-				const appendTo = customStyleTag || @_document.head
-				if (appendTo.querySelector(styleId)) return
-				var style = @element("style");
-				style.id = styleId;
-				style.textContent = "${styles}";
-				@append(appendTo, style);
+				@appendStyleIfNotPresent(customStyleTag || @_document.head, "${component.stylesheet.id}-style", "${styles}");
 			}
 		`);
 	}

src/runtime/internal/dom.ts

@@ -1,5 +1,14 @@
 import { has_prop } from './utils';
 
+export function appendStyleIfNotPresent(target: Element, styleId: string, styles: string) {
+	if (!target.querySelector('#' + styleId)) {
+		const style = element('style');
+		style.id = styleId;
+		style.textContent = styles;
+		append(target, style);
+	}
+}
+
 export function append(target: Node, node: Node) {
 	target.appendChild(node);
 }