In addition to the other answers, you can use this less-known method to grab elements of a certain parent like so,
$('child', 'parent');
In your case, that would be
if ($(event.target, 'div#hello')[0]) console.log(`${event.target.tagName} is an offspring of div#hello`);
Note the use of commas between the child and parent and their separate quotation marks. If they were surrounded by the same quotes
$('child, parent');
you'd have an object containing both objects, regardless of whether they exist in their document trees.