Assigned keys to HTMLElement.dataset are ignored

[tobiasdalhof]

Hey there,

I stumbled upon an issue where assigned keys to HTMLElement.dataset are ignored.

To reproduce the issue, you can extend this test case:

happy-dom/packages/happy-dom/test/nodes/html-element/HTMLElement.test.ts

Line 182 in bda5a7b

describe('get dataset()', () => {

describe('get dataset()', () => {
	it('Returns attributes prefixed with "data-" as an object.', () => {
		element.setAttribute('test1', 'value1');
		element.setAttribute('data-test2', 'value2');
		element.setAttribute('test3', 'value3');
		element.setAttribute('data-test4', 'value4');
		element.dataset.test5 = 'value5'; // Add this line
		expect(element.dataset).toEqual({
			test2: 'value2',
			test4: 'value4',
			test5: 'value5' // Add this line
		});
	});
});