elinks/test/ecmascript/assert/event.html

<script>
var e = new Event('message', { cancelable: true });

console.error('event.html');
console.assert(e.target === null, e.target);
console.assert(e.cancelable, 'cancelable true');
console.assert(!e.defaultPrevented, 'false');
e.preventDefault();
console.assert(e.defaultPrevented, 'true');
console.assert(e.type === 'message', 'message');
console.exit();
</script>