The behaviour you're referring to is actually a global property `window.event` [0]. Although it's part of the DOM spec, it's only there for historical reasons a

The behaviour you're referring to is actually a global property `window.event` [0]. Although it's part of the DOM spec, it's only there for historical reasons and should definitely be avoided. [0]: https://developer.mozilla.org/en-US/docs/Web/API/Window/event https://developer.mozilla.org/en-US/docs/Web/API/Window/even...