web-browser-features-checklist.html

<script type="text/javascript">
function unsupported(name, asserted = false) {
	if (!asserted) {
		document.write(`${name} is not supported.<br />`);
	}
}

function tryFunction(name, value) {
	try {
		Function(value);
		// document.write("+");
	} catch (why) {
		// document.write("-");
		unsupported(name);
	}
	// document.write(name + "<br />");
}

tryFunction('GeneratorFunction', 'function* g(){}');
tryFunction('AsyncFunction', 'async function f(){}');
tryFunction('AsyncGeneratorFunction', 'async function* fg(){}');
tryFunction('EventTarget.constructor', 'new EventTarget');
tryFunction('BigInt', '1n');
tryFunction('for await', 'async function f(){for await (let item of []) {}}');
tryFunction('Static class fields', 'class C {static name = "value"}');
tryFunction('Dynamic class fields', 'class C {name = "value"}');
tryFunction('Generator arrow functions', 'let g = () =>* {}');

class bound {
}
tryFunction('Decorators', `class C {
	@bound render() {
	}
}`);

function tryReference(name) {
	// document.write((window[name] ? '+' : '-') + name + "<br />");
	unsupported(name, window[name]);
}
tryReference('DataTransferItem');
tryReference('DataTransferItemList');
tryReference('BroadcastChannel');
tryReference('VisualViewport');
tryReference('FontFace');
tryReference('customElements');
tryReference('IntersectionObserver');
tryReference('ResizeObserver');

function tryFeature(name, value) {
	// document.write((value ? '+' : '-') + name + "<br />");
	unsupported(name, value);
}
let dummyElement = document.createElement('div');
tryFeature('HTMLElement.prototype.animate', dummyElement.animate);
tryFeature('HTMLElement.prototype.attributeStyleMap', dummyElement.attributeStyleMap);
tryFeature('HTMLElement.prototype.computedStyleMap', dummyElement.computedStyleMap);
tryFeature('Set.prototype.difference(iterable)', (new Set).difference);

tryFeature('HTMLScriptElement.prototype.noModule', document.createElement('script').noModule == false);
</script>