DOM

[Exposed=(Window,Worker,AudioWorklet)]
interface Event { constructor(, optional  = {}); readonly attribute , optional  = false, optional  = false); // legacy
}; dictionary EventInit {  = false;  = false;  = false;
};

An Event object is simply named an event. It allows for
signaling that something has occurred, e.g., that an image has completed downloading.

A potential event target is null or an EventTarget object.

An event has an associated target (a potential event target). Unless stated otherwise it is null.

An event has an associated (a potential event target). Unless stated otherwise it is null.

Other specifications use relatedTarget to define a relatedTarget attribute. [UIEVENTS]

An event has an associated touch target list (a list of zero or more potential event targets). Unless stated otherwise it is the
empty list.

The touch target list is for the exclusive use of defining the TouchEvent interface and related interfaces. [TOUCH-EVENTS]

An event has an associated path. A path is a list of structs. Each struct consists of an invocation target (an EventTarget object), an invocation-target-in-shadow-tree (a boolean), a shadow-adjusted target (a potential event target), a (a potential event target), a touch target list (a list of potential event targets), a root-of-closed-tree (a boolean), and
a slot-in-closed-tree (a boolean). A path is initially
the empty list.