fix(dom): throw if `tagName` is invalid

src/dom/htmlelement.spec.ts

@@ -865,6 +865,25 @@ describe("HtmlElement", () => {
 			expect(result?.tagName).toEqual("b");
 		});
 	});
+
+	it("should not throw error if tagName is undefined", () => {
+		expect.assertions(1);
+		expect(() => new HtmlElement(undefined, null, NodeClosed.EndTag, null, location)).not.toThrow();
+	});
+
+	it("should throw error if tagName is empty string", () => {
+		expect.assertions(1);
+		expect(() => new HtmlElement("", null, NodeClosed.EndTag, null, location)).toThrow(
+			"The tag name provided ('') is not a valid name"
+		);
+	});
+
+	it("should throw error if tagName is asterisk", () => {
+		expect.assertions(1);
+		expect(() => new HtmlElement("*", null, NodeClosed.EndTag, null, location)).toThrow(
+			"The tag name provided ('*') is not a valid name"
+		);
+	});
 });
 
 function mockEntry(stub: Partial<MetaData> = {}): MetaData {

src/dom/htmlelement.ts

@@ -21,6 +21,10 @@ function isElement(node: DOMNode): node is HtmlElement {
 	return node.nodeType === NodeType.ELEMENT_NODE;
 }
 
+function isValidTagName(tagName: string | undefined): boolean {
+	return Boolean(tagName !== "" && tagName !== "*");
+}
+
 export class HtmlElement extends DOMNode {
 	public readonly tagName: string;
 	public readonly parent: HtmlElement | null;
@@ -41,6 +45,10 @@ export class HtmlElement extends DOMNode {
 		const nodeType = tagName ? NodeType.ELEMENT_NODE : NodeType.DOCUMENT_NODE;
 		super(nodeType, tagName, location);
 
+		if (!isValidTagName(tagName)) {
+			throw new Error(`The tag name provided ('${tagName || ""}') is not a valid name`);
+		}
+
 		this.tagName = tagName || "#document";
 		this.parent = parent ?? null;
 		this.attr = {};
@@ -177,9 +185,6 @@ export class HtmlElement extends DOMNode {
 	 * If passing "*" this test will pass if any tagname is set.
 	 */
 	public is(tagName: string): boolean {
-		if (!this.tagName) {
-			return false;
-		}
 		return tagName === "*" || this.tagName.toLowerCase() === tagName.toLowerCase();
 	}