fix: [#1429] Element.insertBefore works when the node is already inse…

…rted
capricorn86 · Jun 3, 2024 · 221e22b · 221e22b
1 parent ef2dfea
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diff --git a/packages/happy-dom/src/nodes/element/ElementUtility.ts b/packages/happy-dom/src/nodes/element/ElementUtility.ts
@@ -137,6 +137,10 @@ export default class ElementUtility {
 		referenceNode: Node | null,
 		options?: { disableAncestorValidation?: boolean }
 	): Node {
+		if (newNode === referenceNode) {
+			return newNode;
+		}
+
 		// NodeUtility.insertBefore() will call appendChild() for the scenario where "referenceNode" is "null" or "undefined"
 		if (newNode[PropertySymbol.nodeType] === NodeTypeEnum.elementNode && referenceNode) {
 			if (

diff --git a/packages/happy-dom/test/nodes/element/Element.test.ts b/packages/happy-dom/test/nodes/element/Element.test.ts
@@ -1247,6 +1247,18 @@ describe('Element', () => {
 			const elements = container.querySelectorAll('p');
 			expect(elements.length).toBe(1);
 		});
+
+		it('Inserts correctly with when adding a children that is already inserted', () => {
+			const container = document.createElement('div');
+			const child = document.createElement('p');
+			child.textContent = 'A';
+			container.appendChild(child);
+
+			container.insertBefore(child, child);
+
+			const elements = container.querySelectorAll('p');
+			expect(elements.length).toBe(1);
+		});
 	});
 
 	describe('get previousElementSibling()', () => {