feat: [#1411] Add queryCommandSupported method.

packages/happy-dom/src/nodes/document/Document.ts

@@ -672,6 +672,20 @@ export default class Document extends Node {
 	public querySelector(selector: string): Element | null {
 		return QuerySelector.querySelector(this, selector);
 	}
+	/**
+	 * Returns true if the command is supported.
+	 * @deprecated
+	 * @param _ Command.
+	 * @returns True if the command is supported, false otherwise.
+	 */
+	public queryCommandSupported(_: string): boolean {
+		if (!arguments.length) {
+			throw new TypeError(
+				"Failed to execute 'queryCommandSupported' on 'Document': 1 argument required, but only 0 present."
+			);
+		}
+		return true;
+	}
 
 	/**
 	 * Returns an elements by class name.

packages/happy-dom/test/nodes/document/Document.test.ts

@@ -599,6 +599,22 @@ describe('Document', () => {
 		});
 	});
 
+	describe('queryCommandSupported', () => {
+		it('Returns true if the command is supported.', () => {
+			// It's just a simple simulation implementation, and it will return true no matter what parameters are passed.
+			expect(document.queryCommandSupported('copy')).toBe(true);
+			expect(document.queryCommandSupported('selectall')).toBe(true);
+		});
+		it('Throws an error if the command is not passed.', () => {
+			// @ts-ignore - Intentionally testing without parameters.
+			expect(() => document.queryCommandSupported()).toThrowError(
+				new TypeError(
+					"Failed to execute 'queryCommandSupported' on 'Document': 1 argument required, but only 0 present."
+				)
+			);
+		});
+	});
+
 	describe('getElementsByClassName()', () => {
 		it('Returns an elements by class name.', () => {
 			const element = document.createElement('div');